Revert "More instruction conversions to *64 and *32."

This reverts commit d5280648fed5dc063ad279cd977a127e5a3f425e.
Revert "const Register& => Register, for header file."

This reverts commit 945fcae8a2718c8359f33af6d901da4270395bf8.
Revert "const Register& => Register."

This reverts commit 91d7744e50da21e19a0f4b65d735a99b5bc78e76.
Revert "Break up some Assembler functions into 32/64 variants to avoid CPURegister."

This reverts commit c76b16851c3a3791d7770e0e4f8bfdaf4b2396e6.