Add instrinsics and patterns for the following instructions:
- bext, bdep, bgrp
Thanks for the patch @dancgr but these intrinsics have already been implemented in D74912. @sdesmalen shared a spreadsheet  with the mailing list to coordinate the intrinsics upstreaming, it's probably not as useful now given they're almost all implemented but you might find it useful if you haven't seen it already.
+sve2-bitperm implies +sve2 so only the former is required.