RFR: 8321010: RISC-V: C2 RoundVF

[Hamlin Li]

Hi,
Can you have a review on this patch to add RoundVF/RoundDF intrinsics?
Thanks!

## Tests

test/hotspot/jtreg/compiler/vectorization/TestRoundVectRiscv64.java test/hotspot/jtreg/compiler/c2/cr6340864/TestFloatVect.java test/hotspot/jtreg/compiler/c2/cr6340864/TestDoubleVect.java test/hotspot/jtreg/compiler/floatingpoint/TestRound.java

test/jdk/java/lang/Math/RoundTests.java

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Commit messages:
 - add tests
 - add test cases
 - v2: (src + 0.5) + rdn
 - Fix corner cases
 - Merge branch 'master' into round-F+D-v
 - refine code
 - RoundVF/D: Initial commit

Changes: https://git.openjdk.org/jdk/pull/17745/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17745&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321010
  Stats: 234 lines in 7 files changed: 230 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/17745.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17745/head:pull/17745

PR: https://git.openjdk.org/jdk/pull/17745