RFR: 8339531: Improve performance of MemorySegment::mismatch [v8]

[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:

  Lower the mismatch threshold

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20848/files
  - new: https://git.openjdk.org/jdk/pull/20848/files/5cccbf40..dc9ad11a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20848&range=07
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20848&range=06-07

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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