[clang] [clang][Interp] Bail out from type-punning casts (PR #163809)

[via cfe-commits]

term-est wrote:

> Use `[clang][bytecode`] in the title please.

Yep. I can fix things up, I think there are formatting issues and cases where legal downcast are rejected as well, which needs more work

I mainly want to get an opinion regarding whether we would want this? I am just getting into the bytecode interpreter and I don't really know about the direction it is heading.

LMK if you want me to pursue this, otherwise I can close the PR


Thank you 🍓 

https://github.com/llvm/llvm-project/pull/163809