Fix PublishAot single warning issue for ProjectReferences (dotnet#101799)

When publishing for native AOT and a ProjectReference has trim/AOT warnings, all the warnings are being collapsed into a single "warning IL2104: Assembly 'X' produced trim warnings."

The issue is that we are using FileName, which cuts off the file extension of the item. But the items we are working with already cut off the `.dll` extension, so it this is cutting off important parts of the assembly name. The fix is to just use Identity, which is the whole item id.

Author: eerhardt

src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets

@@ -281,7 +281,7 @@ The .NET Foundation licenses this file to you under the MIT license.
       <IlcArg Include="@(_IlcRootedAssemblies->'--root:%(Identity)')" />
       <IlcArg Include="@(_IlcConditionallyRootedAssemblies->'--conditionalroot:%(Identity)')" />
       <IlcArg Include="@(_IlcTrimmedAssemblies->'--trim:%(Identity)')" />
-      <IlcArg Include="@(_IlcNoSingleWarnAssemblies->'--nosinglewarnassembly:%(Filename)')" />
+      <IlcArg Include="@(_IlcNoSingleWarnAssemblies->'--nosinglewarnassembly:%(Identity)')" />
       <IlcArg Condition="'$(TrimmerDefaultAction)' == 'copyused' or '$(TrimmerDefaultAction)' == 'copy' or '$(TrimMode)' == 'partial'" Include="--defaultrooting" />
       <IlcArg Include="--resilient" />
       <IlcArg Include="@(UnmanagedEntryPointsAssembly->'--generateunmanagedentrypoints:%(Identity)')" />