[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:

Some initial comments - but I can't see why so much logic is in x86 directly. The keepJumpConditionsTogether implementation appears very generic, and I'd expect it to be in DAGBuilder and x86 just has a simple TLI flag callback to enable it.

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