[One .NET] use **FromWorkload** for targeting/runtime pack versions (d…

…otnet#6184)

Context: dotnet/sdk#19596

If we use the version number string of `**FromWorkload**`, then our
runtime packages don't need to be resolved from a NuGet feed. They can
be resolved from the `dotnet/packs` directory.

This completely eliminates the need for a `NuGet.config` file when
building a .NET 6 app with a local build of the Android workload.

You can simply do:

    ~/android-toolchain/dotnet/dotnet new android
    ~/android-toolchain/dotnet/dotnet build

Documentation/building/unix/instructions.md

@@ -93,22 +93,7 @@ but this is only part of the story. Your local
 local Android "workload" in `Microsoft.Android.Sdk.$(HostOS)` matching
 your operating system.
 
-To use the Android workload, you will need a `NuGet.config`:
-
-```xml
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <packageSources>
-    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
-    <add key="local-xa" value="/full/path/to/bin/BuildDebug/nuget-unsigned" />
-  </packageSources>
-</configuration>
-```
-
-The local package source in the `bin/BuildDebug/nuget-unsigned` directory is
-currently needed for the Android runtime packages.
-
-Then use a `.csproj` file such as:
+Create a new project with `dotnet new android`:
 
 ```xml
 <Project Sdk="Microsoft.NET.Sdk">

Documentation/building/windows/instructions.md

@@ -107,22 +107,7 @@ but this is only part of the story. Your local
 populated with a local Android "workload" in
 `Microsoft.Android.Sdk.$(HostOS)` matching your operating system.
 
-To use the Android workload, you will need a `NuGet.config`:
-
-```xml
-<?xml version="1.0" encoding="utf-8"?>
-<configuration>
-  <packageSources>
-    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
-    <add key="local-xa" value="C:\full\path\to\bin\BuildDebug\nuget-unsigned" />
-  </packageSources>
-</configuration>
-```
-
-The local package source in the `bin\BuildDebug\nuget-unsigned` directory is
-currently needed for the Android runtime packages.
-
-Then use a `.csproj` file such as:
+Create a new project with `dotnet new android`:
 
 ```xml
 <Project Sdk="Microsoft.NET.Sdk">

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

@@ -114,10 +114,10 @@ WARNING:  DO NOT MODIFY this file unless you are knowledgeable about MSBuild and
         Include="Microsoft.Android"
         TargetFramework="$(_AndroidNETAppTargetFramework)"
         RuntimeFrameworkName="Microsoft.Android"
-        DefaultRuntimeFrameworkVersion="$(AndroidPackVersionLong)"
-        LatestRuntimeFrameworkVersion="$(AndroidPackVersionLong)"
+        DefaultRuntimeFrameworkVersion="**FromWorkload**"
+        LatestRuntimeFrameworkVersion="**FromWorkload**"
         TargetingPackName="Microsoft.Android.Ref"
-        TargetingPackVersion="$(AndroidPackVersionLong)"
+        TargetingPackVersion="**FromWorkload**"
         RuntimePackNamePatterns="Microsoft.Android.Runtime.**RID**"
         RuntimePackRuntimeIdentifiers="@(_AndroidNETAppRuntimePackRids, '%3B')"
         Profile="Android"

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Common/XamarinProject.cs

@@ -31,7 +31,7 @@ public abstract class XamarinProject
 		public IList<BuildItem> References { get; private set; }
 		public IList<Package> PackageReferences { get; private set; }
 		public string GlobalPackagesFolder { get; set; } = FileSystemUtils.FindNugetGlobalPackageFolder ();
-		public IList<string> ExtraNuGetConfigSources { get; set; }
+		public IList<string> ExtraNuGetConfigSources { get; set; } = new List<string> ();
 
 		public virtual bool ShouldRestorePackageReferences => PackageReferences?.Count > 0;
 		/// <summary>
@@ -98,12 +98,6 @@ public XamarinProject (string debugConfigurationName = "Debug", string releaseCo
 	</PropertyGroup>
 </Project>"
 				});
-
-				// Feeds only needed for .NET 5+
-				ExtraNuGetConfigSources = new List<string> {
-					Path.Combine (XABuildPaths.BuildOutputDirectory, "nuget-unsigned"),
-					"https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json",
-				};
 			} else {
 				SetProperty (KnownProperties.Configuration, () => Configuration);
 			}