RFR: 8370196: C2: Improve (U)MulHiLNode::MulHiValue

[Zihao Lin]

If nodes both are constant, support constant folding.

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Commit messages:
 - C2: Improve (U)MulHiLNode::MulHiValue

Changes: https://git.openjdk.org/jdk/pull/28097/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28097&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370196
  Stats: 10 lines in 1 file changed: 10 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/28097.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28097/head:pull/28097

PR: https://git.openjdk.org/jdk/pull/28097