Introduce targets to filter target frameworks

Relies on dotnet/msbuild#8350 to be active or not cause build errors when not enabled. This is largely still experimental and may change.
Enables the ability for an invocation of an arcade build to only build a desired set of target frameworks. The primary consumer is source-build. This allows source-build to simply remove TFMs from the build that would require SBRPs without extensive changes in project files.

Author: mmitche

src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeCommonTargets.CrossTargeting.targets

@@ -4,4 +4,5 @@
   <Import Project="$(_ArcadeOverriddenCustomBeforeMicrosoftCommonCrossTargetingTargets)" Condition="Exists('$(_ArcadeOverriddenCustomBeforeMicrosoftCommonCrossTargetingTargets)')"/>
 
   <Import Project="Version.BeforeCommonTargets.targets"/>
+  <Import Project="TargetFrameworkFilters.BeforeCommonTargets.targets"/>
 </Project>

src/Microsoft.DotNet.Arcade.Sdk/tools/BeforeCommonTargets.targets

@@ -8,4 +8,5 @@
   </PropertyGroup>
 
   <Import Project="Version.BeforeCommonTargets.targets"/>
+  <Import Project="TargetFrameworkFilters.BeforeCommonTargets.targets"/>
 </Project>

src/Microsoft.DotNet.Arcade.Sdk/tools/TargetFrameworkFilters.BeforeCommon.targets

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Licensed to the .NET Foundation under one or more agreements. The .NET Foundation licenses this file to you under the MIT license. -->
+<Project>
+  <PropertyGroup>
+    <!-- Obtain the original set based on whether TargetFramework or TargetFrameworks was used -->
+    <_EnableTargetFrameworkFiltering>false</_EnableTargetFrameworkFiltering>
+    <_EnableTargetFrameworkFiltering Condition="'$(NoTargetFrameworkFiltering)' != 'true' and '$(DotNetTargetFrameworkFilter)' != ''">true</_EnableTargetFrameworkFiltering>
+  </PropertyGroup>
+
+  <PropertyGroup Condition="$(_EnableTargetFrameworkFiltering)">
+    <_OriginalTargetFrameworks Condition="'$(TargetFrameworks)' != ''">$(TargetFrameworks)</_OriginalTargetFrameworks>
+    <_OriginalTargetFrameworks Condition="'$(TargetFramework)' != ''">$(TargetFramework)</_OriginalTargetFrameworks>
+    <_FilteredTargetFrameworks>$([MSBuild]::Unescape($([MSBuild]::IntersectTargetFrameworks('$(_OriginalTargetFrameworks)', '$(DotNetTargetFrameworkFilter)'))))</_FilteredTargetFrameworks>
+    <!-- Maintain usage of the original property,  -->
+    <TargetFrameworks Condition="'$(TargetFrameworks)' != ''">$(_FilteredTargetFrameworks)</TargetFrameworks>
+    <TargetFramework Condition="'$(TargetFramework)' != ''">$(_FilteredTargetFrameworks)</TargetFramework>
+    <ExcludeFromBuild Condition="'$(_FilteredTargetFrameworks)' == ''">true</ExcludeFromBuild>
+  </PropertyGroup>
+
+</Project>