[llvm] [clang] [AArch64][SME2] Add ldr_zt, str_zt builtins and intrinsics (PR #72849)

[Matthew Devereau via cfe-commits]

MDevereau wrote:

> It looks like a few other pull requests are changing the same code around ImmToTile. Might be good to land this smaller patch first so you can rebase the others and reduce the diffs!

The idea was that the changes to `ImmToTile` were small and any of my in-flight PRs could land first. But this one is definitely easiest to get in first.

https://github.com/llvm/llvm-project/pull/72849