[AArch64] Create set.fpmr intrinsic and assembly lowering (#114248)
This patch introduces new llvm.set.fpmr intrinsics for setting value in
FPMR register and adds its lowering to series of read-compare-write
instructions. This intrinsic will be generated during lowering of FP8 C
intrinsics into LLVM-IR introduced in later patch.
***This is an experimental implementation of handling fp8 intriniscs and
is likely to change in the future.***