[DynInst_API:] [dyninst/dyninst] 895520: Clean up MachRegister class (#1604)

[Tim Haines <noreply@xxxxxxxxxx>]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: 895520f5c79545c30fb1da0e255288c8a4c36125
      https://github.com/dyninst/dyninst/commit/895520f5c79545c30fb1da0e255288c8a4c36125
  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

  Log Message:
  -----------
  Clean up MachRegister class (#1604)

* Add missing switch breaks in size()

* Add break after assert in case statement

* Move assert into default case in 'size'

This is semantically equivalent, but fixes the 'incomplete without
default' linter warning.

* Add error messages in getROSERegister

I don't know if it's correct to assert in these conditions. This is
semantically equivalent, fixes the 'incomplete without default' linter
warning, and avoids asserting.

* Return InvalidRegister in DwarfEncToReg

This makes them all consisent and fixes the 'incomplete without default'
linter warning.

* Remove dead code

I left the commented-out switch cases. I'm not sure why they aren't
used.

* Remove useless asserts

* Remove 'init_names' declaration

It was never implemented.