clang support for Armv8.8/9.3 HBC

This introduces clang command line support for new Armv8.8-A and
Armv9.3-A Hinted Conditional Branches feature, previously introduced
into LLVM in https://reviews.llvm.org/D116156.

Patch by Tomas Matheson and Son Tuan Vu.

Differential Revision: https://reviews.llvm.org/D116939