Refactoring of our instruction decoding routines and addition of some
missing encodings.

* for-next/insn:
  arm64: insn: avoid circular include dependency
  arm64: insn: move AARCH64_INSN_SIZE into <asm/insn.h>
  arm64: insn: decouple patching from insn code
  arm64: insn: Add load/store decoding helpers
  arm64: insn: Add some opcodes to instruction decoder
  arm64: insn: Add barrier encodings
  arm64: insn: Add SVE instruction class
  arm64: Move instruction encoder/decoder under lib/
  arm64: Move aarch32 condition check functions
  arm64: Move patching utilities out of instruction encoding/decoding