<i18n dev> RFR: JDK-8331646: Add specific regression leap year tests (Task - P4)

[serhiysachkov]

Calendar.add() tests that describe its behavior.

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Commit messages:
 - Merge remote-tracking branch 'origin/JDK-8331646' into JDK-8331646
 - JDK-8331646 adding tests to validate Calendar.add() for leap year
 - JDK-8331646 Add specific regression leap year tests

Changes: https://git.openjdk.org/jdk/pull/19082/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19082&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331646
  Stats: 270 lines in 1 file changed: 270 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19082.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19082/head:pull/19082

PR: https://git.openjdk.org/jdk/pull/19082