[hot reload] Update test infrastructure to consume metadata update handler type ids

[lambdageek]

Depends on dotnet/hotreload-utils#152. For [CreateNewOnMetadataUpdate] types, we would really like to know in unit tests the ids of the new types that get generated in the deltas since the type names are going to be mangled. Once hotreload-utils are updated to serialize the type ids, we need to update ApplyUpdateUtils to read them and make them available to the tests. (And also the test .csproj needs to be updated to bundle the .handler.json files with the app).

Contributes to #57365