[Xamarin.Android.Build.Tasks] case-insensitive Legacy Designer fixup (#8376)

Context: 628d6cb
Context: dc3ccf2

We have a very odd situation with the
[`Xamarin.CommunityToolkit.MauiCompat` NuGet package][0]:

The NuGet package ships with a file `.net/__res_name_case_map.txt`
(628d6cb) in `Xamarin.CommunityToolkit.MauiCompat.aar` which contains
the case map changes for the `@(AndroidResource)` items.  The purpose
of this file is to allow the user to use PascalCase (or any case) names
in C# code, while the Android Resource compilation is left as all
lowercase.  This is because Android requires that file-backed resource
names consist of only lowercase letters.

The contents of this file includes:

	Resources/Layout/CameraFragment.axml;layout/camerafragment.xml

which tells us that the Android `R.layout.camerafragment` resource id
should be "bound" as `Resouce.Layout.CameraFragment`, which allows
[`CameraFragment.android.cs` to build][1]:

	public override AView? OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) =>
	    inflater.Inflate(Resource.Layout.CameraFragment, null);

However, when we look at the IL that comes from the NuGet package we
see the only lowercase `camerafragment`:

	ikdasm ~/.nuget/packages/xamarin.communitytoolkit.mauicompat/2.0.2-preview1013/lib/net6.0-android31.0/Xamarin.CommunityToolkit.MauiCompat.dll| grep Layout::camerafragment
	…
	    IL_0131:  stsfld     int32 Xamarin.CommunityToolkit.MauiCompat.Resource/Layout::camerafragment
	…
	    IL_0001:  ldsfld     int32 Xamarin.CommunityToolkit.MauiCompat.Resource/Layout::camerafragment

For some reason as part of the XamarinCommunityToolkit build
[the following script][2] was run on the code:

	sed -i '' 's/MauiCompat.Resource.Layout.CameraFragment/MauiCompat.Resource.Layout.camerafragment/g' ./src/CommunityToolkit/Xamarin.CommunityToolkit.MauiCompat/**/CameraFragment.android.cs

This changes `Resource.Layout.CameraFragment` to
`Resource.Layout.camerafragment`, apparently because *something* is
renaming [`CameraFragment.axml`][3] to `camerafragment.axml` *after*
`__res_name_case_map.txt` is generated, but before
`CameraFragment.android.cs` is compiled.
The NuGet still includes the `.aar` with the case map changes, which
are now inconsistent with the assembly contents.

I'm not sure why XamarinCommunityToolkit does all this.

The result of the above XamarinCommunityToolkit build and packaging
behavior is that it interacts badly with the new net8.0-android
Resource Designer Assembly (dc3ccf2) work, with a build-time error:

	error XA8000: Could not find Android Resource ‘@layout/camerafragment’. Please update @(AndroidResource) to add the missing resource.

This is because we are looking for the lowercase version of the
resource in the Designer assembly property list, but because of the
remap file we only know about the PascalCase version. 

As a workaround, fallback to a *case-insensitive* resource name
lookup if a case-sensitive lookup fails.

[0]: https://www.nuget.org/packages/Xamarin.CommunityToolkit.MauiCompat/
[1]: https://github.com/xamarin/XamarinCommunityToolkit/blob/5a6062f3c3543acda3c36ca4683cd8fc7fe86ba7/src/CommunityToolkit/Xamarin.CommunityToolkit/Views/CameraView/Android/CameraFragment.android.cs#L129
[2]: https://github.com/xamarin/XamarinCommunityToolkit/blob/5a6062f3c3543acda3c36ca4683cd8fc7fe86ba7/MauiCompat.sh#L561
[3]: https://github.com/xamarin/XamarinCommunityToolkit/blob/5a6062f3c3543acda3c36ca4683cd8fc7fe86ba7/src/CommunityToolkit/Xamarin.CommunityToolkit/Resources/Layout/CameraFragment.axml

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixLegacyResourceDesignerStep.cs

@@ -30,6 +30,7 @@ public class FixLegacyResourceDesignerStep : LinkDesignerBase
 		AssemblyDefinition designerAssembly = null;
 		TypeDefinition designerType = null;
 		Dictionary<string, MethodDefinition> lookup;
+		Dictionary<string, MethodDefinition> lookupCaseInsensitive;
 
 		protected override void EndProcess ()
 		{
@@ -61,7 +62,7 @@ protected override void LoadDesigner ()
 					LogMessage ($"   Did not find {DesignerAssemblyNamespace}.Resource type. It was probably linked out.");
 					return;
 				}
-				lookup = BuildResourceDesignerPropertyLookup (designerType);
+				lookup = BuildResourceDesignerPropertyLookup (designerType, out lookupCaseInsensitive);
 			} finally {
 				designerLoaded = true;
 			}
@@ -105,10 +106,11 @@ internal override bool ProcessAssemblyDesigner (AssemblyDefinition assembly)
 			return true;
 		}
 
-		Dictionary<string, MethodDefinition> BuildResourceDesignerPropertyLookup (TypeDefinition type)
+		Dictionary<string, MethodDefinition> BuildResourceDesignerPropertyLookup (TypeDefinition type, out Dictionary<string, MethodDefinition> caseInsensitiveLookup)
 		{
 			LogMessage ($"     Building Designer Lookups for {type.FullName}");
 			var output = new Dictionary<string, MethodDefinition> (StringComparer.Ordinal);
+			caseInsensitiveLookup = new Dictionary<string, MethodDefinition> (StringComparer.OrdinalIgnoreCase);
 			foreach (TypeDefinition definition in type.NestedTypes)
 			{
 				foreach (PropertyDefinition property in definition.Properties)
@@ -117,7 +119,9 @@ Dictionary<string, MethodDefinition> BuildResourceDesignerPropertyLookup (TypeDe
 					if (output.ContainsKey (key)) {
 						LogMessage ($"          Found duplicate {key}");
 					} else {
+						LogMessage ($"          Adding {key}");
 						output.Add (key, property.GetMethod);
+						caseInsensitiveLookup [key] = property.GetMethod;
 					}
 				}
 			}
@@ -153,7 +157,12 @@ protected override void FixBody (MethodBody body, TypeDefinition designer)
 				if (idx >= 0) {
 					string key = line.Substring (idx + designerFullName.Length);
 					LogMessage ($"Looking for {key}.");
-					if (lookup.TryGetValue (key, out MethodDefinition method)) {
+					var found = lookup.TryGetValue (key, out MethodDefinition method);
+					if (!found) {
+						LogMessage ($"DEBUG! Failed to find {key}! Trying case insensitive lookup.");
+						found = lookupCaseInsensitive.TryGetValue (key, out method);
+					}
+					if (found) {
 						var importedMethod = designer.Module.ImportReference (method);
 						var newIn = Instruction.Create (OpCodes.Call, importedMethod);
 						instructions.Add (i, newIn);