RFR: 8331427: Rename confusingly named ArraysSupport.signedHashCode

[Pavel Rappo]

Please review this trivial method rename. While this issue was originally spotted in [another PR], it makes sense to address it separately. Test results are pending; not that I expect failures, but still.

[another PR]: https://github.com/openjdk/jdk/pull/14831#issuecomment-1655477396

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/19023/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19023&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331427
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19023.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19023/head:pull/19023

PR: https://git.openjdk.org/jdk/pull/19023