RFR: 8339531: Improve performance of MemorySegment::mismatch [v4]

[Per Minborg]

> This PR proposes to improve the performance of `MemorySegment::mismatch` by using Java code rather than transitioning to native code.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Add optimized checking

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20848/files
  - new: https://git.openjdk.org/jdk/pull/20848/files/14184901..c421c620

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20848&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20848&range=02-03

  Stats: 89 lines in 2 files changed: 83 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/20848.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20848/head:pull/20848

PR: https://git.openjdk.org/jdk/pull/20848