In objdump, many targets support `-M no-aliases`. Instead of having a
`-*-no-aliases` for each target when LLVM adds the support, it makes more sense
to introduce objdump style `-M`.
-riscv-arch-reg-names is removed. -riscv-no-aliases has too many uses and thus is retained for now.
Reviewed By: luismarques
Differential Revision: https://reviews.llvm.org/D103004