[llvm] [X86] Don't always seperate conditions in `(br (and/or cond0, cond1))` into seperate branches (PR #81689)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

Mostly there, my remaining concern is how this is supposed to interact with middle-end passes like SimplfyCFG which are handling something similar?

https://github.com/llvm/llvm-project/pull/81689