[Xamarin.Android.Build.Tasks] do not use %(HintPath)

[jonathanpeppers]

We noticed some odd behavior from MSBuild such as:

ReferenceDependencyPaths
    C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\MonoAndroid\v1.0\Facades\netstandard.dll
        HintPath = ..\..\..\packages\Newtonsoft.Json.11.0.2\lib\netstandard2.0\Newtonsoft.Json.dll
    C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\Common7\IDE\ReferenceAssemblies\Microsoft\Framework\MonoAndroid\v1.0\System.Runtime.Serialization.dll
        HintPath = ..\..\..\packages\Xamarin.Forms.3.1.0.583944\lib\MonoAndroid10\Xamarin.Forms.Platform.Android.dll

%(HintPath) is leftover metadata from the @(ReferencePath) item
group, so it points to the original assembly???

We currently use %(HintPath) in two places, but it seems like we
don't need to use it at all? @(ReferencePath) and
@(ReferenceDependencyPaths) will both have the full path to all of
the assemblies in ITaskItem.ItemSpec.

I was able to simplify two of our tasks and just use ItemSpec:

• <ResolveLibraryProjectImports/>
• <GenerateResourceDesigner/>

I also did some general refactoring in <GenerateResourceDesigner/>:

• Reorganized the top-level foreach loop, to more closely match what
  we were already doing in <ResolveLibraryProjectImports/>.
• Cleaned up some general LINQ usage.
• A List<string> of assembly names could just be a
  List<AssemblyDefinition>, to avoid some LINQ.
• Fixed spelling/used string interpolation in log messages.

Results

I think I'm seeing a ~50ms improvement in
<GenerateResourceDesigner/> for an initial build:

Before:
205 ms  GenerateResourceDesigner                   1 calls
After:
152 ms  GenerateResourceDesigner                   1 calls

Future Work

• It might be worth porting <GenerateResourceDesigner/> to use
  System.Reflection.Metadata instead of Mono.Cecil at some point.

[jonathanpeppers]

FYI I asked about in #msbuild on Slack, the thought is:

• @(ReferenceDependencyPaths) is just inheriting all metadata from the original @(ReferencePath) item group.
• They are afraid to change %(HintPath) on @(ReferenceDependencyPaths) because someone might be relying on it now...