[X86][MC][CodeGen] Support EGPR for KMOV (#73781)

KMOV is essential for copy between k-registers and GPRs.
R16-R31 was added into GPRs in #70958, so we extend KMOV for these new
registers first.

This patch
1.  Promotes KMOV instructions from VEX space to EVEX space
2.  Emits prefix {evex} for the EVEX variants
3. Prefers EVEX variant than VEX variant in ISEL and optimizations for
better RA

EVEX variants will be compressed to VEX variants by existing EVEX2VEX
pass if no EGPR is used.

RFC:
https://discourse.llvm.org/t/rfc-design-for-apx-feature-egpr-and-ndd-support/73031/4
TAG: llvm-test-suite && CPU2017 can be built with feature egpr
successfully.