[clang] [CIR][AArch64] Implement vget_lane_bf16 and vgetq_lane_bf16 builtins (PR #186866)

[Andrzej Warzyński via cfe-commits]

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banach-space wrote:

> I think that the order is preserved, it is just diffed in a strange way
You are right, sorry about that!

> I don't have commit access yet, you can merge it

Sure, could you resolve the merge conflicts? I've merged a few changes today, so apologies in advance if that's my fault.

https://github.com/llvm/llvm-project/pull/186866