[llvm] [AArch64][PAC] Lower authenticated calls with ptrauth bundles. (PR #85736)

[Ahmed Bougacha via llvm-commits]

ahmedbougacha wrote:

I rebased this on top of main and extracted the couple of common helper functions from the auth/resign isel patch, to not depend on it.

> LGTM with a few const-related comments left

Thanks, all of these should be addressed now.  I'll leave this open for another day or two if anyone wants to chime in, either way we can iterate further in tree

https://github.com/llvm/llvm-project/pull/85736