[AArch64] Add __ARM_FEATURE_BTI and __ARM_FEATURE_PAUTH

Macros are added to ACLE[1] and already added to ARM but these two are missing from AArch64.

[1] https://github.com/ARM-software/acle/blob/main/main/acle.md#changes-between-acle-q3-2021-and-acle-q4-2021

Reviewed By: chill

Differential Revision: https://reviews.llvm.org/D139445