[RFC] Exempt input type and value validation from BC Break policy

Hi all, Thanks for the RFC. I have a real‑world example that seems to fit this “input validation” category and wanted to sanity‑check it with you. I opened PR #21319 to promote a few ext/snmp invalid‑input warnings to ValueError (only for invalid inputs). Valid inputs behave the same; the goal is just to make errors catchable and consistent with other extensions. If this RFC passes, would a change like that be OK without a separate per‑function RFC? And are there any expectations you’d want contributors to follow (tests, deprecation note, minor vs major timing)? Happy to share more details if needed. Thanks, Pratik