[foreign-memaccess+abi] RFR: 8290880: Add static MemorySegment::mismatch method

[Maurizio Cimadamore]

As discussed in [1], it would be useful if the `MemorySegment` class provided a static mismatch method, similarly to what we have provided for `copy`.

This patch adds that method, and rewrites the existing instance `mismatch` method to be based on that new static method.
It then adds new tests to cover the new static method.

[1] - https://mail.openjdk.org/pipermail/panama-dev/2022-June/017099.html

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Commit messages:
 - Tweak javadoc
 - Initial push

Changes: https://git.openjdk.org/panama-foreign/pull/691/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=691&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290880
  Stats: 199 lines in 3 files changed: 147 ins; 30 del; 22 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/691.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/691/head:pull/691

PR: https://git.openjdk.org/panama-foreign/pull/691