Use separate images

Commit 1d38470 worked, in that we
no longer get insta-crashes on Windows!
The `System.Runtime.CompilerServices.Unsafe` crash was fixed!

We now turn our attention to the XA0102 warnings, which are *also*
responsible for errors in `BuildReleaseArm64()`, because the `.apk`
size now differs, because the icons are now larger; `.apk` size
increased by 31,744 bytes!

…which is why SixLabors.ImageSharp was used…

Avoid SixLabors.ImageSharp and instead have
`Xamarin.ProjectTools` use the same icons as the
`dotnet new android` template, in
`src\Microsoft.Android.Templates\android\Resources\**\appicon.png`.
In order to ensure sane `%(LogicalName)` values, `%(RecrusiveDir)`
is used as part of the logical name, resulting in resource names
on macOS such as:

  * `mipmap-hdpi/appicon.png`
  * `mipmap-mdpi/appicon.png`
  * `mipmap-xhdpi/appicon.png`
  * `mipmap-xxhdpi/appicon.png`
  * `mipmap-xxxhdpi/appicon.png`

I'm not sure what Windows will do offhand, so have
Xamarin.ProjectTools.dll *also* look for a resource name with
`/` replaced by `\` (`Path.DirectorySeparatorChar`) so that this
logic *should* work on Windows as well.

Hopefully this will resolve the XA0102 warnings and the
`BuildReleaseArm64()` errors.

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/XamarinAndroidCommonProject.cs

@@ -19,14 +19,26 @@ public abstract class XamarinAndroidCommonProject : XamarinAndroidProject
 
 		static XamarinAndroidCommonProject ()
 		{
-			var stream = typeof(XamarinAndroidCommonProject).Assembly.GetManifestResourceStream ("Xamarin.ProjectTools.Resources.Base.Icon.png");
-			icon_binary_mdpi = new byte [stream.Length];
-			stream.Read (icon_binary_mdpi, 0, (int) stream.Length);
+			icon_binary_mdpi    = GetResourceContents ("mipmap-mdpi/appicon.png");
+			icon_binary_hdpi    = GetResourceContents ("mipmap-hdpi/appicon.png");
+			icon_binary_xhdpi   = GetResourceContents ("mipmap-xhdpi/appicon.png");
+			icon_binary_xxhdpi  = GetResourceContents ("mipmap-xxhdpi/appicon.png");
+			icon_binary_xxxhdpi = GetResourceContents ("mipmap-xxxhdpi/appicon.png");
+		}
 
-			icon_binary_hdpi    = icon_binary_mdpi;
-			icon_binary_xhdpi   = icon_binary_mdpi;
-			icon_binary_xxhdpi  = icon_binary_mdpi;
-			icon_binary_xxxhdpi = icon_binary_mdpi;
+		static byte[] GetResourceContents (string resourceName)
+		{
+			var assembly    = typeof (XamarinAndroidCommonProject).Assembly;
+			var stream      = assembly.GetManifestResourceStream (resourceName) ??
+				assembly.GetManifestResourceStream (resourceName.Replace ('/', Path.DirectorySeparatorChar));
+			if (stream == null) {
+				return Array.Empty<byte>();
+			}
+			using (stream) {
+				var contents    = new byte [stream.Length];
+				stream.Read (contents, 0, (int) stream.Length);
+				return contents;
+			}
 		}
 
 		protected XamarinAndroidCommonProject (string debugConfigurationName = "Debug", string releaseConfigurationName = "Release")

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Xamarin.ProjectTools.csproj

@@ -14,6 +14,9 @@
     <Compile Remove="Resources\**\*.cs" />
     <Compile Include="..\..\..\..\bin\Build$(Configuration)\XABuildConfig.cs" />
     <EmbeddedResource Include="Resources\**\*" />
+    <EmbeddedResource Include="..\..\..\Microsoft.Android.Templates\android\Resources\**\appicon.png">
+      <LogicalName>%(RecursiveDir)appicon.png</LogicalName>
+    </EmbeddedResource>
   </ItemGroup>
   <ItemGroup>
     <Content Include="..\..\..\..\.nuget\NuGet.exe">