The point of this commit is only to generate code and make sure it's
valid as far as compiling and linking are concerned. The code has not
been tested at run time as not all the infrastructure on the
Xamarin.Android side is implemented yet. This is on purpose, to keep PRs
smaller.

The majority of this PR introduces various classes, enums and structures
related to code generation. Support for various LLVM IR instructions is
limited only to those we actually use and only to elements of those
constructions that we use. As such, it's not a general purpose code
generator which allows us to make some assumptions and take some
shortcuts (without compromising correctness and validity of the
generated code)

Portions of the PR (the native type handling system) are to be treated
as proof-of-concept as they are not as optimized (design wise) as they
should be. The reason for this limitation is that it requires modifying
the previous LLVM IR data generation code and it would contribute to
this PR's already substantial size. The next PR in the series will take
care of that rewrite as well as it will focus on implementing the
runtime side of marshal methods, making it possible to actually run
applications which use marshal methods.

What this PR implements is the following:

  * LLVM IR
    * function and instruction attributes
    * function parameter (declaration/definition) and argument (runtime)
      handling
    * function variable (including parameters) handling, including
      unnamed local variables
    * support for native function signatures and pointers to functions
    * The ret, store, load, icmp, br, call and phi instructions
  * Marshal method generator
    * managed to JNI signature and symbol name translations

Implement missing runtime support so that applications are able to
actually run.  Also fix issues with marshal method overloads as well as
add code to handle the case where two unrelated methods (from different
types) end up using the same JNI symbol name:

  * `Java_crc64e1fb321c08285b90_CellAdapter_n_1onActionItemClicked
    * `System.Boolean Android.Views.ActionMode/ICallback::OnActionItemClicked(Android.Views.ActionMode,Android.Views.IMenuItem)`
    * `System.Boolean AndroidX.AppCompat.View.ActionMode/ICallback::OnActionItemClicked(AndroidX.AppCompat.View.ActionMode,Android.Views.IMenuItem)`

* main:
  LEGO: Merge pull request 7221
  LEGO: Merge pull request 7219
  [Xamarin.Android.Build.Tasks] use `ToJniName(type, cache)` (dotnet#7211)
  [docs] Synchronize with MicrosoftDocs/xamarin-docs (dotnet#7208)
  [Mono.Android] Remove System.Linq usage (dotnet#7210)
  Bump to Android NDK r25 (dotnet#6764)
  Bump to mono/opentk@daa9b2d5 (dotnet#7192)
  [Mono.Android] Optional NTLMv2 support in AndroidMessageHandler (dotnet#6999)
  Bump to dotnet/installer@53587f9 7.0.100-rc.1.22374.1 (dotnet#7198)

* mm-codegen:
  LEGO: Merge pull request 7221
  LEGO: Merge pull request 7219
  [Xamarin.Android.Build.Tasks] use `ToJniName(type, cache)` (dotnet#7211)
  [docs] Synchronize with MicrosoftDocs/xamarin-docs (dotnet#7208)
  [Mono.Android] Remove System.Linq usage (dotnet#7210)
  Bump to Android NDK r25 (dotnet#6764)
  Bump to mono/opentk@daa9b2d5 (dotnet#7192)
  [Mono.Android] Optional NTLMv2 support in AndroidMessageHandler (dotnet#6999)
  Bump to dotnet/installer@53587f9 7.0.100-rc.1.22374.1 (dotnet#7198)

* main:
  Bump to dotnet/java-interop@a5756ca8. (dotnet#7226)
  Bump `$(AndroidNet6Version)` to 32.0.447 (dotnet#7224)

* mm-codegen:
  Bump to dotnet/java-interop@a5756ca8. (dotnet#7226)
  Bump `$(AndroidNet6Version)` to 32.0.447 (dotnet#7224)

Also, deal with duplicate native symbol names

* main:
  [Mono.Android] fix crash on startup with EnableLLVM (dotnet#7188)
  [ci] Add Android Designer test template (dotnet#7227)

* mm-codegen:
  [Mono.Android] fix crash on startup with EnableLLVM (dotnet#7188)
  [ci] Add Android Designer test template (dotnet#7227)

* main:
  [Localization] Import translated resx files (dotnet#7190)

* mm-codegen:
  [Localization] Import translated resx files (dotnet#7190)

Hit a snag with one of the callbacks using non-blittable
arguments (`bool` in this case), but it seems to be the last (famous
last words) obstacle preventing the app from starting.

A handful of hacks are needed ATM, too.

* main:
  [build] update to latest JDKs (dotnet#7236)

* mm-codegen:
  [build] update to latest JDKs (dotnet#7236)

Unfortunately, 133 out of 182 methods are still registered dynamically,
the reason being that they either return `bool` or take it as one of
their parameters. `bool` isn't a blittable type and thus such methods
cannot be used with `[UnregisteredCallersOnly]`. To move farther, we
need to modify the generator to stop generating native callbacks (just
them) with `bool`.

* main:
  Bump to dotnet/installer@8f63969 7.0.100-rc.1.22407.1 (dotnet#7217)

* mm-codegen:
  Bump to dotnet/installer@8f63969 7.0.100-rc.1.22407.1 (dotnet#7217)

* main:
  [ci] Upload test assemblies after signing (dotnet#7241)

* mm-codegen:
  [ci] Upload test assemblies after signing (dotnet#7241)

Beginnings of the generator

The app still crashes for some reason (appears something is not
decorated with the `[UnmanagedCallersOnly]` attribute) but the IL code
generation is complete and the app doesn't report any native/runtime
linking errors.

TBC next week

* main:
  Bump to xamarin/monodroid@210073e1 (dotnet#7272)
  [OneLoc] Localize Microsoft.Android.Templates (dotnet#7248)
  [README] Add links to XA 13.0 release installers (dotnet#7251)
  Bump to dotnet/installer@716bd17 7.0.100-rc.1.22409.23 (dotnet#7247)
  Bump manifest-merger from 30.2.1 to 30.2.2 (dotnet#7238)

* mm-codegen:
  Bump to xamarin/monodroid@210073e1 (dotnet#7272)
  [OneLoc] Localize Microsoft.Android.Templates (dotnet#7248)
  [README] Add links to XA 13.0 release installers (dotnet#7251)
  Bump to dotnet/installer@716bd17 7.0.100-rc.1.22409.23 (dotnet#7247)
  Bump manifest-merger from 30.2.1 to 30.2.2 (dotnet#7238)

MAUI hello world works now

* main:
  [ci] disable `<XamarinTelemetry/>` task (dotnet#7275)
  [Xamarin.Android.Build.Tasks] Use marshal-ilgen component (dotnet#7260)

* mm-codegen:
  [ci] disable `<XamarinTelemetry/>` task (dotnet#7275)
  [Xamarin.Android.Build.Tasks] Use marshal-ilgen component (dotnet#7260)

* main:
  [xabuild] update binding redirects for MSBuild 17.3 (dotnet#7273)

* mm-codegen:
  [xabuild] update binding redirects for MSBuild 17.3 (dotnet#7273)

* mm-codegen:
  Disable some debug CWLs

We can now report names of the mathods and classes that we failed
to look up.

* main:
  Bump to dotnet/installer@f3da421 7.0.100-rc.2.22417.1 (dotnet#7255)

* mm-codegen:
  Escape double quotes in function attribute value
  Bump to dotnet/installer@f3da421 7.0.100-rc.2.22417.1 (dotnet#7255)

* main:
  [Xamarin.Android.Build.Tasks, monodroid] LLVM-IR Generator (dotnet#7163)
  $(AndroidPackVersionSuffix)=rc.2; net7 is 33.0.0.rc.2 (dotnet#7283)
  [ci] Add EXE files to windows-toolchain-pdb artifact (dotnet#7279)

These are now handled by the wrapper generator

* main:
  Bump r8 from 3.3.28 to 3.3.75 (dotnet#7292)
  [Xamarin.Android.Build.Tasks] Pass `hybrid` to AOT, if enabled (dotnet#7263)
  Bump to lz4/lz4@5ff83968 [v1.9.4] (dotnet#7262)
  [Mono.Android] add "built-in" delegate for MAUI+non-Shell (dotnet#7267)

* main:
  [xaprepare] Generate SourceLink.json (dotnet#7298)

* main:
  Bump to dotnet/installer@84d26a0 7.0.100-rc.2.22419.24 (dotnet#7294)
  Bump to xamarin/java.interop/main@e31d9c62 (dotnet#7266)

* main:
  [tests] disable `$(_FastDeploymentDiagnosticLogging)` in PerformanceTest (dotnet#7307)

* main:
  [ci] Split up signing for files to be notarized (dotnet#7321)
  [ci] Add support to net7.0 for multi-targeting in VS (dotnet#7311)
  [ci] Skip classic tests on .NET release branches (dotnet#7312)
  [tests] Use `$(AndroidSdkPlatformToolsVersion)`=33.0.3 (dotnet#7320)
  Bump to xamarin/java.interop/main@4f813cb2 (dotnet#7308)
  Bump to mono/mono.posix@d8994ca, dotnet/android-libzipsharp@98e9173 (dotnet#7309)

* main:
  Bump to dotnet/installer@2d1a4de 7.0.100-rc.2.22426.5 (dotnet#7314)
  [FabricBot] Apply 'needs-triage' label to new issues. (dotnet#7327)
  [Mono.Android] .NET 6+ & GetHttpMessageHandler & null, oh my! (dotnet#7214)

* main:
  [FabricBot] Add `possibly-stale` GitHub label for closing old issues (dotnet#7343)
  Don't use Dictionary<K,V> to avoid duplicate value exception (dotnet#7340)
  [One .NET] fix `dotnet run -c Release` (dotnet#7341)

* main:
  Bump to dotnet/installer@330dee3 (dotnet#7334)
  [xaprepare] CGManifest.json conforms to JSON schema (dotnet#7342)