[RISCV] Add support for XCVbi extension in CV32E40P

Implement XCVbi intrinsics for CV32E40P according to the specification.

This commit is part of a patch-set to upstream the 7 vendor specific extensions of CV32E40P.

Contributors: @CharKeaney, @jeremybennett, @lewis-revill, @liaolucy, Nandni Jamnadas, @paolos, @simoncook, @xmj.

bf2ad26b originally commited.
e4777dc4 reverted due to test failures caused by a merge conflict marker in llvm/test/CodeGen/RISCV/attributes that was accidentally checked in.
This commit removed the conflict marker and recommitted.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D154412