[sve][acle] Enable feature macros for SVE ACLE extensions.

Summary:
The following feature macros have been added:

__ARM_FEATURE_SVE_BF16

__ARM_FEATURE_SVE_MATMUL_INT8

__ARM_FEATURE_SVE_MATMUL_FP32

__ARM_FEATURE_SVE_MATMUL_FP64

The driver has been updated to enable them accordingly to the value of
the target feature passed at command line.

The SVE ACLE tests using the macros have been modified to work with
the target feature instead of passing the macro at command line.

Reviewers: sdesmalen, efriedma, c-rhodes, kmclaughlin, SjoerdMeijer, rengolin

Subscribers: tschuett, kristof.beyls, rkruppe, psnobl, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D82623