Remove the file extension in CreateBlazorTrimmerRootDescriptorFile (#23330)

The linker doesn't resolve assemblies correctly if the file extension (.dll) is included in the assembly name in the descriptor xml file.

See also dotnet/linker#1294

Author: eerhardt

src/Razor/Microsoft.NET.Sdk.Razor/src/CreateBlazorTrimmerRootDescriptorFile.cs

@@ -32,7 +32,9 @@ internal void WriteRootDescriptor(Stream stream)
             var roots = new XElement("linker");
             foreach (var assembly in Assemblies)
             {
-                var assemblyName = assembly.GetMetadata("FileName") + assembly.GetMetadata("Extension");
+                // NOTE: Descriptor files don't include the file extension
+                // in the assemblyName.
+                var assemblyName = assembly.GetMetadata("FileName");
                 var typePreserved = assembly.GetMetadata("Preserve");
                 var typeRequired = assembly.GetMetadata("Required");