[AArch64][SME2] Add the IR intrinsics for SME2 fclamp, sclamp and uclamp instructions

Adds intrinsics for the following SME2 instructions:

* fclamp (2 and 4 vectors)
* sclamp (2 and 4 vectors)
* uclamp (2 and 4 vectors)

I've added these new instructions to the existing sve2p1-* tests
because although they are included as part of SME2 they are still
SVE-like, in that they only operate on SVE vectors.

NOTE: These intrinsics are still in development and are subject to future changes.

Differential Revision: https://reviews.llvm.org/D142355