Treat ValidationAttribute on generic methods as Validated

[kzu]

Summary

• Recognize a generic method annotated with any ValidationAttribute subclass as if it also had [Validated].
• Register the closed type arguments and return type at each call site, including wrappers up to eight levels.

Test plan

• Closure test: a custom ValidationAttribute on a generic factory and wrapper registers the closed return type.
• Closure test: the same attribute on a non-generic method, and an unrelated attribute on a generic method, do not register closed types.
• dotnet test (27 passed)

[kzu]

🧪 Details on Ubuntu 24.04.5 LTS

from retest v1.1.0 on .NET 10.0.12 with 💜 by @devlooped