[llvm] IR: Allow vector type in atomic load and store (PR #117625)

[via llvm-commits]

jofrn wrote:

| We can land the verifier change separately, but only after a non-x86-specific patch for backend support is available as well.
Okay, split https://github.com/llvm/llvm-project/pull/111414 into itself and https://github.com/llvm/llvm-project/pull/118793.

https://github.com/llvm/llvm-project/pull/117625