RFR: 8378833: Improve offset arithmetic in ArraysSupport::mismatch

[Raffaello Giulietti]

Some of the `ArraysSupport::mismatch` family of methods compute offsets using a mix of `int` and `long` arithmetic.
This can lead to wrong results, which are then passed as arguments to an intrinsic method or to a Java method using `Unsafe`.

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Commit messages:
 - 8378833: Improve offset arithmetic in ArraysSupport::mismatch

Changes: https://git.openjdk.org/jdk/pull/29957/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29957&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8378833
  Stats: 13 lines in 1 file changed: 0 ins; 0 del; 13 mod
  Patch: https://git.openjdk.org/jdk/pull/29957.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29957/head:pull/29957

PR: https://git.openjdk.org/jdk/pull/29957