chore(ci): Revert temporary Windows CI generated code hacks

[macastelaz]

Added to get #13715 to pass windows CI learned that these window CI failures are just being ignored/accepted since the issue is upstream.

[gemini-code-assist]

Code Review

This pull request performs a large-scale refactoring across two Java modules. In the java-backstory module, it removes the java_outer_classname option from udm.proto and updates all generated Java classes to reference com.google.backstory.Udm instead of UdmProto. In the java-cloudsecuritycompliance module, it removes numerous @Nullable annotations and their corresponding imports from generated clients, settings, stubs, and resource name classes, enforcing non-nullability across these APIs. Additionally, some redundant type arguments in gRPC calls have been cleaned up. No review comments were provided, so there is no further feedback to address.