[Xamarin.Android.Build.Tasks] lazily populate Resource lookup (#7686)

Fixes: #7684

Comparing .NET 7 to main, I noticed:

    .NET 7
    Task LinkAssembliesNoShrink 4ms
    main/.NET 8
    Task LinkAssembliesNoShrink 101ms

Under `dotnet trace` a lot of the time was spent in:

    94.74ms MonoDroid.Tuner.FixLegacyResourceDesignerStep.LoadDesigner()

Reviewing the code, I think we can "lazily" call the `LoadDesigner()`
method. Now it delays until the `ProcessAssemblyDesigner()` method. I
had to reorder logic slightly to do this.

I also updated one log message to only log duplicates, as it was
logging hundreds of lines:

    if (output.ContainsKey (key)) {
        LogMessage ($"          Found duplicate {key}");
    } else {
        output.Add (key, property.GetMethod);
    }

Which also showed up in `dotnet trace`:

    25.58ms Microsoft.Android.Build.Tasks.MSBuildExtensions.LogDebugMessage()

With these changes, I instead get:

    Task LinkAssembliesNoShrink 5ms

Which is probably ~the same performance as before or plenty good enough!

Lastly, I also removed some other code & members in
`FixLegacyResourceDesignerStep` that Visual Studio showed me was
unused.

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

@@ -21,20 +21,8 @@ public class FixLegacyResourceDesignerStep : LinkDesignerBase
 	{
 		internal const string DesignerAssemblyName = "_Microsoft.Android.Resource.Designer";
 		internal const string DesignerAssemblyNamespace = "Microsoft.Android.Resource.Designer";
-#if ILLINK
-		protected override void Process ()
-		{
-			cache = Context;
-		}
-#else // ILLINK
-		public FixLegacyResourceDesignerStep (IMetadataResolver cache)
-		{
-			this.cache = cache;
-		}
 
-		readonly
-#endif // ILLINK
-		IMetadataResolver cache;
+		bool designerLoaded = false;
 		AssemblyDefinition designerAssembly = null;
 		TypeDefinition designerType = null;
 		Dictionary<string, MethodDefinition> lookup;
@@ -49,35 +37,34 @@ protected override void EndProcess ()
 
 		protected override void LoadDesigner ()
 		{
-			if (designerAssembly != null)
+			if (designerLoaded)
 				return;
-			var designerNameAssembly = AssemblyNameReference.Parse ($"{DesignerAssemblyName}, Version=1.0.0.0");
 			try {
-				designerAssembly = Resolve (designerNameAssembly);
-			} catch (Mono.Cecil.AssemblyResolutionException) {
-				LogMessage ($"   Could not resolve assembly {DesignerAssemblyName}.");
-			} catch (System.IO.FileNotFoundException) {
-				LogMessage ($"   Assembly {DesignerAssemblyName} did not exist.");
-			}
-			if (designerAssembly == null) {
-				return;
-			}
-			designerType = designerAssembly.MainModule.GetTypes ().FirstOrDefault (x => x.FullName == $"{DesignerAssemblyNamespace}.Resource");
-			if (designerType == null) {
-				LogMessage ($"   Did not find {DesignerAssemblyNamespace}.Resource type. It was probably linked out.");
-				return;
+				var designerNameAssembly = AssemblyNameReference.Parse ($"{DesignerAssemblyName}, Version=1.0.0.0");
+				try {
+					designerAssembly = Resolve (designerNameAssembly);
+					LogMessage ($"   Loaded {designerNameAssembly}");
+				} catch (Mono.Cecil.AssemblyResolutionException) {
+					LogMessage ($"   Could not resolve assembly {DesignerAssemblyName}.");
+				} catch (System.IO.FileNotFoundException) {
+					LogMessage ($"   Assembly {DesignerAssemblyName} did not exist.");
+				}
+				if (designerAssembly == null) {
+					return;
+				}
+				designerType = designerAssembly.MainModule.GetTypes ().FirstOrDefault (x => x.FullName == $"{DesignerAssemblyNamespace}.Resource");
+				if (designerType == null) {
+					LogMessage ($"   Did not find {DesignerAssemblyNamespace}.Resource type. It was probably linked out.");
+					return;
+				}
+				lookup = BuildResourceDesignerPropertyLookup (designerType);
+			} finally {
+				designerLoaded = true;
 			}
-			lookup = BuildResourceDesignerPropertyLookup (designerType);
-			return;
 		}
 
 		internal override bool ProcessAssemblyDesigner (AssemblyDefinition assembly)
 		{
-			if (designerAssembly == null || designerType == null) {
-				LogMessage ($"   Not using {DesignerAssemblyName}");
-				return false;
-			}
-
 			if (!FindResourceDesigner (assembly, mainApplication: false, out TypeDefinition designer, out CustomAttribute designerAttribute)) {
 				LogMessage ($"   {assembly.Name.Name} has no designer. ");
 				return false;
@@ -90,6 +77,15 @@ internal override bool ProcessAssemblyDesigner (AssemblyDefinition assembly)
 				return false;
 			}
 
+			// This is expected for the first call, in <LinkAssembliesNoShrink/>
+			if (!designerLoaded)
+				LoadDesigner ();
+
+			if (designerAssembly == null || designerType == null) {
+				LogMessage ($"   Not using {DesignerAssemblyName}");
+				return false;
+			}
+
 			LogMessage ($"    Adding reference {designerAssembly.Name.Name}.");
 			assembly.MainModule.AssemblyReferences.Add (designerAssembly.Name);
 			var importedDesignerType = assembly.MainModule.ImportReference (designerType.Resolve ());
@@ -114,9 +110,10 @@ Dictionary<string, MethodDefinition> BuildResourceDesignerPropertyLookup (TypeDe
 				foreach (PropertyDefinition property in definition.Properties)
 				{
 					string key = $"{definition.Name}::{property.Name}";
-					if (!output.ContainsKey (key)) {
-						LogMessage ($"          Adding {key}");
-						output.Add(key, property.GetMethod);
+					if (output.ContainsKey (key)) {
+						LogMessage ($"          Found duplicate {key}");
+					} else {
+						output.Add (key, property.GetMethod);
 					}
 				}
 			}

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

@@ -112,7 +112,7 @@ static Pipeline CreatePipeline (LinkerOptions options)
 			// end monodroid specific
 
 			if (options.UseDesignerAssembly)
-				pipeline.AppendStep (new FixLegacyResourceDesignerStep (cache));
+				pipeline.AppendStep (new FixLegacyResourceDesignerStep ());
 			pipeline.AppendStep (new FixAbstractMethodsStep (cache));
 			pipeline.AppendStep (new MonoDroidMarkStep (cache));
 			pipeline.AppendStep (new SweepStep ());

src/Xamarin.Android.Build.Tasks/Tasks/LinkAssembliesNoShrink.cs

@@ -66,9 +66,7 @@ public override bool RunTask ()
 				var cache = new TypeDefinitionCache ();
 				var fixAbstractMethodsStep = new FixAbstractMethodsStep (resolver, cache, Log);
 				var addKeepAliveStep = new AddKeepAlivesStep (resolver, cache, Log, UsingAndroidNETSdk);
-				var fixLegacyResourceDesignerStep = new FixLegacyResourceDesignerStep (resolver, cache, Log);
-				if (UseDesignerAssembly)
-					fixLegacyResourceDesignerStep.Load ();
+				var fixLegacyResourceDesignerStep = new FixLegacyResourceDesignerStep (resolver, Log);
 				for (int i = 0; i < SourceFiles.Length; i++) {
 					var source = SourceFiles [i];
 					var destination = DestinationFiles [i];
@@ -133,17 +131,12 @@ class FixLegacyResourceDesignerStep : MonoDroid.Tuner.FixLegacyResourceDesignerS
 			readonly DirectoryAssemblyResolver resolver;
 			readonly TaskLoggingHelper logger;
 
-			public FixLegacyResourceDesignerStep (DirectoryAssemblyResolver resolver, TypeDefinitionCache cache, TaskLoggingHelper logger)
-				: base (cache)
+			public FixLegacyResourceDesignerStep (DirectoryAssemblyResolver resolver, TaskLoggingHelper logger)
 			{
 				this.resolver = resolver;
 				this.logger = logger;
 			}
 
-			public void Load () {
-				LoadDesigner ();
-			}
-
 			public override void LogMessage (string message)
 			{
 				logger.LogDebugMessage ("{0}", message);