RFR: 8321283: Reuse StringLatin1::equals in regionMatches

[Francesco Nigro]

This improvement has been found on https://github.com/vert-x3/vertx-web/pull/2526.

It can potentially affect the existing ArraysSupport.mismatch caller code-path performance ie requires investigation.

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Commit messages:
 - Reduce the amount of conditions
 - Reuse StringLatin1::equals in regionMatches

Changes: https://git.openjdk.org/jdk/pull/16933/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16933&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321283
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16933.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16933/head:pull/16933

PR: https://git.openjdk.org/jdk/pull/16933