[AArch64] Generalize the instruction size checking in AsmPrinter (llvm#110108)

Most of PAuth-related code counts the instructions being inserted and
asserts that no more bytes are emitted than the size returned by the
getInstSizeInBytes(MI) method. This check seems useful not only for
PAuth-related instructions. Also, reimplementing it globally in
AArch64AsmPrinter makes it more robust and simplifies further
refactoring of PAuth-related code.

Author: atrosinenko