[AArch64][PAC] Support BLRA* instructions in SLS Hardening pass (llvm#98062)

Make SLS Hardening pass handle BLRA* instructions the same way it
handles BLR. The thunk names have the form

    __llvm_slsblr_thunk_xN            for BLR thunks
    __llvm_slsblr_thunk_(aaz|abz)_xN  for BLRAAZ and BLRABZ thunks
    __llvm_slsblr_thunk_(aa|ab)_xN_xM for BLRAA and BLRAB thunks

Now there are about 1800 possible thunk names, so do not rely on linear
thunk function's name lookup and parse the name instead.

This patch reapplies llvm#97605.

Author: atrosinenko