[llvm] [AArch64][ISel] Add support for v8.4a RCpc `ldapur`/`stlur` (PR #67879)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

Added GISel tests, rebased to main, and dropped unneeded specialized support in GISel for `stlur`, as the execution within the match table will correctly perform the pattern match and replacement (was already happening for `ldapur`).

https://github.com/llvm/llvm-project/pull/67879