[AArch64] Add support for various operations on nxv1i1 types.

The supported operations are:
* Logical operations (and, or, xor, bic)
* Logical reductions (and, or, xor, [us]min, [us]max)
* Conversions to/from svbool_t
* Predicate count (CNTP)

Reviewed By: paulwalker-arm

Differential Revision: https://reviews.llvm.org/D128835