[RISCV][Clang] Add some RVV Permutation intrinsic functions.

Support the following instructions.
1. Vector Slide Instructions
2. Vector Register Gather Instructions
3. Vector Compress Instruction

Authored-by: Roger Ferrer Ibanez <rofirrim@gmail.com>
Co-Authored-by: Zakk Chen <zakk.chen@sifive.com>

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D100127