RFR: 8320995: RISC-V: C2 PopCountVI

[Hamlin Li]

Hi,
Can you help to review this patch?
Both auto-vect and vector api depends on this intrinsic.
Thanks!

## Performance
Not performance test was done, as this depends on vcpop.v instruction in zvbb extension and the code seqeunce is rather simple than non-intrinsic version.

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Commit messages:
 - move vcpop_v
 - fix Zvbb flag and misc
 - remove unexpected local files
 - fix issue for mask version
 - Merge branch 'master' into popcount-v
 - merge master; fix issues
 - minor fix
 - merge master
 - PopCountV: Initial commit

Changes: https://git.openjdk.org/jdk/pull/19065/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19065&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320995
  Stats: 92 lines in 11 files changed: 80 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/19065.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19065/head:pull/19065

PR: https://git.openjdk.org/jdk/pull/19065