RFR: 8302163: Speed up various String comparison methods with ArraysSupport.mismatch

Mon Feb 13 10:12:14 UTC 2023

We can improve various String methods such as `startsWith`, `endsWith` and `regionMatches` by leveraging the intrinsified mismatch methods in `ArraysSupport`.

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Commit messages:
 - Remove overlapping micros, extend testing to endsWith, regionCI and some minor improvements to String::regionMatches
 - Expand micro coverage
 - Add micro from @eirbjo
 - Revert UTF16.compareValues
 - Add a few micros, apply optimization to StringUTF16.compareValues
 - Speed up various String comparison methods with ArraysSupport.mismatch

Changes: https://git.openjdk.org/jdk/pull/12528/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12528&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302163
  Stats: 170 lines in 5 files changed: 105 ins; 44 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/12528.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12528/head:pull/12528

PR: https://git.openjdk.org/jdk/pull/12528