[NativeAot] Start running S.R.Metadata tests (#76583)

* Check if S.R.Metadata tests now pass

This was hitting a compiler crash due to System.Reflection.Metadata bug around generic attributes. Since we now host the compiler with RC1 bits, the problem should be gone.

No merge for now because this should not be promoted to a smoke test, just unblocked in the extra-platforms run.

* Update tests.proj

Author: MichalStrehovsky

src/libraries/tests.proj

@@ -480,7 +480,6 @@
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Net.Mail\tests\Functional\System.Net.Mail.Functional.Tests.csproj"
                       Condition="'$(TargetOS)' == 'windows'"/>
 
-    <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Reflection.Metadata\tests\System.Reflection.Metadata.Tests.csproj" />
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Net.Http.Json\tests\FunctionalTests\System.Net.Http.Json.Functional.Tests.csproj" />
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Linq.Parallel\tests\System.Linq.Parallel.Tests.csproj" />
     <ProjectExclusions Include="$(MSBuildThisFileDirectory)System.Text.Json\tests\System.Text.Json.Tests\System.Text.Json.Tests.csproj" />