enable async in Libraries

Author: VSadov

src/libraries/Directory.Build.props

@@ -101,4 +101,8 @@
     <CoverageIncludeDirectory Include="shared\Microsoft.NETCore.App\$(ProductVersion)" />
   </ItemGroup>
 
+  <PropertyGroup>
+    <Features Condition="'$(RuntimeFlavor)' != 'mono' and '$(TestBuildMode)' != 'nativeaot' and '$(TargetArchitecture)' != 'wasm'">$(Features);runtime-async=on</Features>
+  </PropertyGroup>
+  
 </Project>