Refactoring the ZoneRules cache for ZoneOffset. Making the cache field final ensures the class can be converted into a value class in the future
------------- Commit messages: - initial commit Changes: https://git.openjdk.org/jdk/pull/30384/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=30384&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8346133 Stats: 14 lines in 1 file changed: 7 ins; 4 del; 3 mod Patch: https://git.openjdk.org/jdk/pull/30384.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/30384/head:pull/30384 PR: https://git.openjdk.org/jdk/pull/30384
