RFR: 8310192: RISC-V: Merge vector min & max instructs with similar match rules

[Gui Cao]

Hi, We merged vector min and max instructions with similar matching rules in this PR, and modified some comments of the copy_memory function in stubGenerator_riscv.cpp.

Please take a look and have some reviews. Thanks a lot.

## Testing:
- [x] Tier1 tests (release)
- [x] Tier2 tests (release)
- [x] Tier3 tests (release)
- [x] test/jdk/jdk/incubator/vector (fastdebug)

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Commit messages:
 - RISC-V: Merge vector min & max instructs with similar match rules

Changes: https://git.openjdk.org/jdk/pull/14510/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14510&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310192
  Stats: 134 lines in 4 files changed: 12 ins; 97 del; 25 mod
  Patch: https://git.openjdk.org/jdk/pull/14510.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14510/head:pull/14510

PR: https://git.openjdk.org/jdk/pull/14510