RFR: 8355699: RISC-V: support SUADD/SADD/SUSUB/SSUB

[Hamlin Li]

Hi,
Can you help to review this patch to add SUADD/SADD/SUSUB/SSUB for vector api?

Thanks!

## Test

running in progress ...

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/25005/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25005&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355699
  Stats: 168 lines in 4 files changed: 146 ins; 1 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/25005.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25005/head:pull/25005

PR: https://git.openjdk.org/jdk/pull/25005