[DynInst_API:] [dyninst/dyninst] 362d5f: Improve name handling in MachRegister (#1612)

[Tim Haines <noreply@xxxxxxxxxx>]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: 362d5f84f7221efca440d53673f36f2b52707f90
      https://github.com/dyninst/dyninst/commit/362d5f84f7221efca440d53673f36f2b52707f90
  Author: Tim Haines <thaines.astro@xxxxxxxxx>
  Date:   2023-10-30 (Mon, 30 Oct 2023)

  Changed paths:
    M common/h/registers/MachRegister.h
    M common/src/registers/MachRegister.C
    M instructionAPI/src/ArchSpecificFormatters.C

  Log Message:
  -----------
  Improve name handling in MachRegister (#1612)

* Clean up name caching in MachRegister

This just needs to be a file-scope static. It also doesn't need to be
allocated on the heap or be an ordered container.

* Fix broken transient include

* Have 'name' return ref to const

No need to make a copy.

* Add back error handling for missing name