[llvm] [AArch64] Use `ZIP1/2` over `INS` for vector concat (PR #142427)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

INS is actually faster than a Q register ZIP on some cores.  For example, Cortex-A55.  Not sure how much we care about this.

https://github.com/llvm/llvm-project/pull/142427