[clang][CIR] Add lowering for fp16 intrinsics (#194865)
This PR adds lowering for the following intrinsic groups:
* https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#absolute-difference-1
* https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#reciprocal-estimate-1
* https://arm-software.github.io/acle/neon_intrinsics/advsimd.html#reciprocal-estimate-1
It also moves the corresponding tests from:
* clang/test/CodeGen/AArch64/v8.2a-fp16-intrinsics.c
to:
* clang/test/CodeGen/AArch64/neon/fullfp16.c
The lowering follows the existing implementation in
CodeGen/TargetBuiltins/ARM.cpp.
