Drop API 31 packs & remove android-32 workload

You should still be able to target `net6.0-android31`, as I hardcoded
the version to what is released on NuGet.org:

https://www.nuget.org/packages/Microsoft.Android.Ref.31/31.0.101-preview.11.117

With these changes `net6.0-android31` resolves from:

    ~\.nuget\packages\microsoft.android.ref.31\31.0.101-preview.11.117\ref\net6.0\Mono.Android.dll

But with `net6.0-android` (defaults to 32 now), you get:

    dotnet\packs\Microsoft.Android.Ref.32\*\ref\net6.0\Mono.Android.dll

I also removed `%(DefaultRuntimeFrameworkVersion)` from
`@(KnownFrameworkReference)` as it is not needed.

Author: jonathanpeppers

build-tools/create-packs/Microsoft.Android.Sdk.proj

@@ -118,18 +118,23 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
   <PropertyGroup>
     <AndroidNETSdkVersion>$(AndroidPackVersionLong)</AndroidNETSdkVersion>
     <XamarinAndroidVersion>$(AndroidPackVersionLong)</XamarinAndroidVersion>
-    <_AndroidRuntimePackId Condition=" '%24(TargetPlatformVersion)' != '$(AndroidLatestUnstableApiLevel).0' ">$(AndroidLatestStableApiLevel)</_AndroidRuntimePackId>
-    <_AndroidRuntimePackId Condition=" '%24(TargetPlatformVersion)' == '$(AndroidLatestUnstableApiLevel).0' ">$(AndroidLatestUnstableApiLevel)</_AndroidRuntimePackId>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '%24(TargetPlatformVersion)' == '31.0' ">
+    <_AndroidRuntimePackId>31</_AndroidRuntimePackId>
+    <_AndroidRuntimePackVersion>31.0.101-preview.11.117</_AndroidRuntimePackVersion>
+  </PropertyGroup>
+  <PropertyGroup>
+    <_AndroidRuntimePackId Condition=" '%24(_AndroidRuntimePackId)' == '' ">$(AndroidLatestStableApiLevel)</_AndroidRuntimePackId>
+    <_AndroidRuntimePackVersion Condition=" '%24(_AndroidRuntimePackVersion)' == '' ">**FromWorkload**</_AndroidRuntimePackVersion>
   </PropertyGroup>
   <ItemGroup>
     <KnownFrameworkReference
         Include="Microsoft.Android"
         TargetFramework="$(_AndroidNETAppTargetFramework)"
         RuntimeFrameworkName="Microsoft.Android"
-        DefaultRuntimeFrameworkVersion="**FromWorkload**"
-        LatestRuntimeFrameworkVersion="**FromWorkload**"
+        LatestRuntimeFrameworkVersion="%24(_AndroidRuntimePackVersion)"
         TargetingPackName="Microsoft.Android.Ref.%24(_AndroidRuntimePackId)"
-        TargetingPackVersion="**FromWorkload**"
+        TargetingPackVersion="%24(_AndroidRuntimePackVersion)"
         RuntimePackNamePatterns="Microsoft.Android.Runtime.%24(_AndroidRuntimePackId).**RID**"
         RuntimePackRuntimeIdentifiers="@(_AndroidNETAppRuntimePackRids, '%3B')"
         Profile="Android"

src/Xamarin.Android.Build.Tasks/Microsoft.NET.Sdk.Android/WorkloadManifest.in.json

@@ -5,27 +5,15 @@
       "description": ".NET SDK Workload for building Android applications.",
       "packs": [
         "Microsoft.Android.Sdk",
-        "Microsoft.Android.Ref.31",
-        "Microsoft.Android.Runtime.31.android-arm",
-        "Microsoft.Android.Runtime.31.android-arm64",
-        "Microsoft.Android.Runtime.31.android-x86",
-        "Microsoft.Android.Runtime.31.android-x64",
-        "Microsoft.Android.Templates"
-      ],
-      "platforms": [ "win-x64", "linux-x64", "osx-x64", "osx-arm64" ],
-      "extends" : [ "microsoft-net-runtime-android" ]
-    },
-    "android-32": {
-      "description": "Preview support for Android API-32.",
-      "packs": [
         "Microsoft.Android.Ref.32",
         "Microsoft.Android.Runtime.32.android-arm",
         "Microsoft.Android.Runtime.32.android-arm64",
         "Microsoft.Android.Runtime.32.android-x86",
-        "Microsoft.Android.Runtime.32.android-x64"
+        "Microsoft.Android.Runtime.32.android-x64",
+        "Microsoft.Android.Templates"
       ],
       "platforms": [ "win-x64", "linux-x64", "osx-x64", "osx-arm64" ],
-      "extends" : [ "android" ]
+      "extends" : [ "microsoft-net-runtime-android" ]
     },
     "android-aot": {
       "description": ".NET SDK Workload for building Android applications with AOT support.",
@@ -45,26 +33,6 @@
         "linux-x64": "Microsoft.Android.Sdk.Linux"
       }
     },
-    "Microsoft.Android.Ref.31": {
-      "kind": "framework",
-      "version": "@WORKLOAD_VERSION@"
-    },
-    "Microsoft.Android.Runtime.31.android-arm": {
-      "kind": "framework",
-      "version": "@WORKLOAD_VERSION@"
-    },
-    "Microsoft.Android.Runtime.31.android-arm64": {
-      "kind": "framework",
-      "version": "@WORKLOAD_VERSION@"
-    },
-    "Microsoft.Android.Runtime.31.android-x86": {
-      "kind": "framework",
-      "version": "@WORKLOAD_VERSION@"
-    },
-    "Microsoft.Android.Runtime.31.android-x64": {
-      "kind": "framework",
-      "version": "@WORKLOAD_VERSION@"
-    },
     "Microsoft.Android.Ref.32": {
       "kind": "framework",
       "version": "@WORKLOAD_VERSION@"