[AArch64] Assembly support for VMSA

Virtual Memory System Architecture (VMSA)

This is part of the 2022 A-Profile Architecture extensions and adds support for
the following:

 - Translation Hardening Extension (FEAT_THE)
 - 128-bit Page Table Descriptors (FEAT_D128)
 - 56-bit Virtual Address (FEAT_LVA3)
 - Support for 128-bit System Registers (FEAT_SYSREG128)
 - System Instructions that can take 128-bit inputs (FEAT_SYSINSTR128)
 - 128-bit Atomic Instructions (FEAT_LSE128)
 - Permission Indirection Extension (FEAT_S1PIE, FEAT_S2PIE)
 - Permission Overlay Extension (FEAT_S1POE, FEAT_S2POE)
 - Memory Attribute Index Enhancement (FEAT_AIE)

New instructions added:
 - FEAT_SYSREG128 adds MRRS and MSRR.
 - FEAT_SYSINSTR128 adds the SYSP instruction and TLBIP aliases.
 - FEAT_LSE128 adds LDCLRP, LDSET, and SWPP instructions.
 - FEAT_THE adds the set of RCW* instructions.

Specs for individual instructions can be found here:
https://developer.arm.com/documentation/ddi0602/2022-09/Base-Instructions/

Contributors:
  Keith Walker
  Lucas Prates
  Sam Elliott
  Son Tuan Vu
  Tomas Matheson

Differential Revision: https://reviews.llvm.org/D138920