winch: Standardize method naming convention accross the assemblers (bytecodealliance#9918)

The initial convention was to name all the methods after the
instructions they represent (e.g., fn mov_ir). This convention has
diverged over time, most noticeably in the AArch64 assembler.

The intention of this commit is primarily for bookkeeping purposes, in
order to maintain a consistent naming convention.

Author: saulecabrera