[clang] [AArch64][Clang] Refactor code to emit SVE & SME builtins (PR #70959)

[Kerry McLaughlin via cfe-commits]

kmclaughlin-arm wrote:

This patch was originally committed in #70662, but it was reverted as it was missing updates to the acle_sve2p1_st1.c & acle_sve2p1_stnt1.c tests.

The first commit in this pull request contains the original patch and the second contains the updated tests.

https://github.com/llvm/llvm-project/pull/70959