[AArch64] Combine subtract with borrow to SBC. (#165271)
Specifically, this patch adds the following combines:
SUB x, (CSET LO, (CMP a, b)) -> SBC x, 0, (CMP a, b)
SUB (SUB x, y), (CSET LO, (CMP a, b)) -> SBC x, y, (CMP a, b)
The CSET may be preceded by a ZEXT.
Fixes #164748.
