<i18n dev> RFR: 8345668: ZoneOffset.ofTotalSeconds performance regression

[Naoto Sato]

The change made in [JDK-8288723](https://bugs.openjdk.org/browse/JDK-8288723) seems innocuous, but it caused this performance regression. Partially reverting the change (ones that involve `computeIfAbsent()`) to the original. Provided a benchmark that iterates the call to `ZoneOffset.ofTotalSeconds(0)` 1,000 times, which improves the operation time from 3,946ns to 2,241ns.

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Commit messages:
 - initial commit

Changes: https://git.openjdk.org/jdk/pull/22854/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22854&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8345668
  Stats: 78 lines in 4 files changed: 69 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/22854.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22854/head:pull/22854

PR: https://git.openjdk.org/jdk/pull/22854