Unify and future-proof Assembly*Attributes with Constants

One more unification and this is likely the last one.
Rather than a custom generator for assembly info attributes, we leverage MSBuild (similar to how the Metadata package does it) to transform the same set of attributes and turn them into @(Constant) items.

Now that custom and dynamic roots are possible, this is really straightforward and should be 100% backwards compatible.

In the future, if additional aseembly-level attributes matching the `Assembly[Name]Attribute` convention are added to the SDK, they will be surfaced automatically as well.

src/ThisAssembly.AssemblyInfo/ThisAssembly.AssemblyInfo.csproj

@@ -4,8 +4,7 @@
     <TargetFramework>netstandard2.0</TargetFramework>
     <LangVersion>latest</LangVersion>
     <IsRoslynComponent>true</IsRoslynComponent>
-    <!-- This generator supports VB too -->
-    <PackFolder>analyzers/dotnet/roslyn$(ThisAssemblyMinimumRoslynVersion)</PackFolder>
+    <PackBuildOutput>false</PackBuildOutput>
   </PropertyGroup>
 
   <PropertyGroup>
@@ -28,30 +27,18 @@ on the `ThisAssembly.Info` class.
     </Description>
   </PropertyGroup>
 
-  <PropertyGroup Label="SponsorLink">
-    <CustomAfterMicrosoftCSharpTargets>$(MSBuildThisFileDirectory)..\SponsorLink\SponsorLink.Analyzer.targets</CustomAfterMicrosoftCSharpTargets>
-    <FundingPackageId>ThisAssembly;$(PackageId)</FundingPackageId>
-  </PropertyGroup>
+  <ItemGroup>
+    <None Remove="ThisAssembly.AssemblyInfo.targets" />
+  </ItemGroup>
 
   <ItemGroup>
     <PackageReference Include="NuGetizer" Version="1.2.2" />
-
-    <PackageReference Include="Scriban" Version="5.10.0" Pack="false" IncludeAssets="build" />
-    <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />
-    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
-
-    <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" Pack="false" />
-    <PackageReference Include="PolySharp" Version="1.14.1" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup>
-    <InternalsVisibleTo Include="ThisAssembly.Tests" />
+    <ProjectReference Include="..\ThisAssembly.Constants\ThisAssembly.Constants.csproj" />
   </ItemGroup>
 
-  <Target Name="VerifySponsorLink" AfterTargets="Build">
-    <Error Condition="'$(SponsorLinkImported)' != 'true'" Text="SponsorLink was not imported." />
-  </Target>
-
   <Import Project="..\Shared\Shared.projitems" Label="Shared" />
 
 </Project>

src/ThisAssembly.AssemblyInfo/ThisAssembly.AssemblyInfo.targets

@@ -1,6 +1,4 @@
 <Project>
-  <Import Project="..\..\buildTransitive\Devlooped.Sponsors.targets" Condition="Exists('..\..\buildTransitive\Devlooped.Sponsors.targets')"/>
-
   <ItemGroup>
     <CompilerVisibleProperty Include="ThisAssemblyNamespace" />
 
@@ -12,4 +10,19 @@
     <FundingPackageId Include="ThisAssembly.AssemblyInfo" />
   </ItemGroup>
 
+  <Target Name="PrepareAssemblyInfoConstants"
+          BeforeTargets="PrepareConstants"
+          DependsOnTargets="GetAssemblyAttributes">
+    <ItemGroup>
+      <AssemblyInfoAttribute Include="@(AssemblyAttribute)"
+                             Exclude="System.Reflection.AssemblyMetadataAttribute;System.Reflection.AssemblyMetadata"
+                             Condition="$([MSBuild]::ValueOrDefault('%(Identity)', '').StartsWith('System.Reflection.Assembly')) == 'true'">
+        <Name>$([MSBuild]::ValueOrDefault('%(Identity)', '').Substring(26).Replace('Attribute', ''))</Name>
+      </AssemblyInfoAttribute>
+    </ItemGroup>
+    <ItemGroup>
+      <Constant Include="@(AssemblyInfoAttribute -> 'Info.%(Name)')" Value="%(AssemblyInfoAttribute._Parameter1)" Root="." />
+    </ItemGroup>
+  </Target>
+
 </Project>