`aarch32`: Orphan instance

[langston-barrett]

We should either disable this warning with a note on why we think this orphan is acceptable, or we should move it to the module that defines RegContext.

src/Data/Macaw/AArch32/Symbolic/Regs.hs:81:1: warning: [GHC-90177] [-Worphans]
    Orphan family instance:
      type instance MS.ArchRegContext SA.AArch32 = RegContext
                      -- Defined at src/Data/Macaw/AArch32/Symbolic/Regs.hs:81:15
    Suggested fix:
      Move the instance declaration to the module of the type family or of the type, or
      wrap the type with a newtype and declare the instance on the new type.
   |
81 | type instance MS.ArchRegContext SA.AArch32 = RegContext
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

See:

• https://ghc.gitlab.haskell.org/ghc/doc/users_guide/using-warnings.html#ghc-flag-Worphans
• https://ghc.gitlab.haskell.org/ghc/doc/users_guide/separate_compilation.html#orphan-modules

[RyanGlScott]

I certainly think this is acceptable, as it is already established convention to define orphan ArchRegContext instances in the macaw subpackages that comprise each ISA. For instance, see this similar orphan instance in macaw-ppc. The instance in macaw-ppc already enables -Wno-orphans—it looks like we just forgot to do the same in macaw-aarch32.