Revert "Download and include runtime packs"

This reverts commit 6bd1b0e.

This idea doesn't fully work yet, see:

dotnet/sdk#14044

It partially works for Android, you can do:

    > .\bin\dotnet\dotnet build .\samples\HelloMaui\HelloMaui.Android\HelloMaui.Android.csproj

But it fails if you set `$(RuntimeIdentifier)`:

    > .\bin\dotnet\dotnet build .\samples\HelloMaui\HelloMaui.Android\HelloMaui.Android.csproj -r android.21-arm
    ...
    error NU1101: Unable to find package Microsoft.Android.Runtime.android.21-arm. No packages exist with this id in source(s): Microsoft Visual Studio Offline Packages, nuget.org

I think the first one only works because we set
`$(RuntimeIdentifiers)` *plural* by default--targeting two RIDs. There
is some special `restore` logic running when you define
`$(RuntimeIdentifier)` *singular*.

Directory.Build.props

@@ -4,11 +4,8 @@
     <PackageVersion>0.1.0-alpha1</PackageVersion>
     <DotNetVersionBand>6.0.100</DotNetVersionBand>
     <DotNetVersion>$(DotNetVersionBand)-preview.1.21103.13</DotNetVersion>
-    <!-- After bumping $(DotNetVersion) find this version in bin/dotnet/sdk/*/dotnet.runtimeconfig.json -->
-    <DotNetRuntimeVersion>6.0.0-preview.1.21102.12</DotNetRuntimeVersion>
     <MicrosoftAndroidVersion>11.0.200-ci.master.85</MicrosoftAndroidVersion>
     <MicrosoftiOSVersion>14.3.100-ci.main.1079</MicrosoftiOSVersion>
-
     <!-- Paths -->
     <MauiOutputPath>$(MSBuildThisFileDirectory)bin/</MauiOutputPath>
     <DotNetDirectory>$(MauiOutputPath)dotnet/</DotNetDirectory>

samples/nuget.config

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+  <packageSources>
+    <clear />
+    <!-- ensure only the sources defined below are used -->
+    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
+    <add key="xamarin" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/xamarin-impl/nuget/v3/index.json" />
+    <add key="public"  value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-public/nuget/v3/index.json" />
+  </packageSources>
+</configuration>

src/DotNet.Toolchain/DotNet.Toolchain.csproj

@@ -5,7 +5,7 @@
       _DownloadDotNetInstallScript;
       _InstallDotNet;
       _AcquireWorkloads;
-      _AcquirePacks;
+      _AcquireSdks;
       _CreateWorkloadSentinel;
     </_ProvisionDependsOn>
   </PropertyGroup>
@@ -47,11 +47,11 @@
     <RemoveDir Directories="@(_WorkloadDirectoriesToDelete);$(DotNetSdkManifestsDirectory)Microsoft.Build.NoTargets" />
     <Touch Files="$(DotNetSdkManifestsDirectory).stamp" AlwaysCreate="true" />
   </Target>
-  <Target Name="_AcquirePacks"
-      Inputs="$(MSBuildAllProjects);../Maui.Dependencies/Maui.Dependencies.Packs.csproj"
+  <Target Name="_AcquireSdks"
+      Inputs="$(MSBuildAllProjects);../Maui.Dependencies/Maui.Dependencies.Sdks.csproj"
       Outputs="$(DotNetPacksDirectory).stamp">
     <Exec
-        Command="&quot;$(DotNetToolPath)&quot; build &quot;$(MSBuildThisFileDirectory)../Maui.Dependencies/Maui.Dependencies.Packs.csproj&quot; -bl:../../bin/Maui.Dependencies.Packs.binlog"
+        Command="&quot;$(DotNetToolPath)&quot; build &quot;$(MSBuildThisFileDirectory)../Maui.Dependencies/Maui.Dependencies.Sdks.csproj&quot; -bl:../../bin/Maui.Dependencies.Sdks.binlog"
         EnvironmentVariables="NUGET_PACKAGES=$(DotNetPacksDirectory)"
     />
     <RemoveDir Directories="$(DotNetPacksDirectory)Microsoft.Build.NoTargets" />

src/Maui.Dependencies/Maui.Dependencies.Sdks.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.Build.NoTargets">
+  <PropertyGroup>
+    <TargetFramework>net6.0</TargetFramework>
+  </PropertyGroup>
+  <ItemGroup>
+    <PackageDownload Include="Microsoft.Android.Ref"            Version="[$(MicrosoftAndroidVersion)]" />
+    <PackageDownload Include="Microsoft.Android.Sdk.win-x64"    Version="[$(MicrosoftAndroidVersion)]" Condition="$([MSBuild]::IsOSPlatform('windows'))" />
+    <PackageDownload Include="Microsoft.Android.Sdk.osx-x64"    Version="[$(MicrosoftAndroidVersion)]" Condition="$([MSBuild]::IsOSPlatform('osx'))" />
+    <PackageDownload Include="Microsoft.Android.Sdk.BundleTool" Version="[$(MicrosoftAndroidVersion)]" />
+    <PackageDownload Include="Microsoft.iOS.Ref" Version="[$(MicrosoftiOSVersion)]" />
+    <PackageDownload Include="Microsoft.iOS.Sdk" Version="[$(MicrosoftiOSVersion)]" />
+  </ItemGroup>
+</Project>

src/Maui.Dependencies/nuget.config

@@ -2,7 +2,6 @@
 <configuration>
   <packageSources>
     <clear />
-    <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
     <add key="xamarin" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/xamarin-impl/nuget/v3/index.json" />
   </packageSources>
 </configuration>