)

Context: #8800
Context: 8bc7a3e
Context: 6836818
Context: libunwind/libunwind#702

Begin adding native method call tracing infrastructure based on
[libunwind][0], initially used in tracing the reasons for why
[Blazor][1] apps break when LLVM marshal methods are enabled
(8bc7a3e, 6836818).  The utility of such infrastructure, however,
is beyond just that particular task; it should be available for
general use by both us and applications.

Method call tracing support is not enabled by default.
To enable it, set the `$(_AndroidEnableNativeStackTracing)` MSBuild
property to `true`.  This will enable the ability to print native, 
managed and Java stack traces by invoking the `monodroid_log_traces`
function from either managed or native application code.

Additionally, change the directory layout for native code.

Previously, `src/monodroid` would produce *five* native libs:

  * `libmono-android.debug.so`
  * `libmono-android.release.so`
  * `libxa-internal-api.so`
  * `libxamarin-app.so`
  * `libxamarin-debug-app-helper.so`

This made for a large `src/monodroid/CMakeLists.txt`, complicating
maintenance.  We had considered trying to move these into separate
`src/LIBRARY-NAME` directories, but it makes things easier with
CMake if we introduce an intermediate directory.

Introduce a new `src/native` directory, to hold native binaries:

  * `src/native/monodroid`: new location for `libmono-android.*.so`

  * `src/native/xamarin-debug-app-helper`: source for
    `libxamarin-debug-app-helper.so`, containing code moved from
    previous `src/monodroid`

  * `src/native/xamarin-app-stub`: source for the "stub"
    `libxamarin-app.so`; the "real" one is produced in the app build.

Some `src/native/*` directories produce libraries (`.so` files). and
some produce *static* archives (`.a` files) to simplify using code
across native libraries.

A [cmake-presets file][2] is processed by `xaprepare`, to create a
`src/native/CMakePresets.json` which contains all the version-specific
bits replacements such as Android API levels, paths to utilities etc.

Developers can create a `src/native/CMakeUserPresets.json` file to
provide local modifications to config options within
`src/native/CMakePresets.json.in`.

Other changes:

  * `src/native/libunwind/fixes/aarch64/Gos-linux.c` is an altered
    copy of [`libunwind/src/aarch64/Gos-linux.c`][3] in order to
    workaround libunwind/libunwind#702.

  * *Begin* turning some instance member functions into static member
    functions, as we don't otherwise need instances of those classes.

  * Begin using `std::source_location` for better crash messages,
    instead of using `__FILE__` and `__LINE__`.

  * Fix endless recursion from a typo in `Util::ends_with()` overload.

[0]: https://github.com/libunwind/libunwind
[1]: https://learn.microsoft.com/aspnet/core/blazor/hybrid/tutorials/maui?view=aspnetcore-8.0
[2]: https://cmake.org/cmake/help/latest/manual/cmake-presets.7.html
[3]: https://github.com/libunwind/libunwind/blob/9cc4d98b22ae57bc1d8c253988feb85d4298a634/src/aarch64/Gos-linux.c