RFR: 8348880: Replace ConcurrentMap with AtomicReferenceArray for ZoneOffset.MINUTES_15_CACHE [v3]

[Shaojin Wen]

> ZoneOffset.MINUTES_15_CACHE uses AtomicReferenceArray to replace ConcurrentMap to avoid object allocation caused by boxing from int to Integer during access.

Shaojin Wen has updated the pull request incrementally with two additional commits since the last revision:

 - simplify
 - MINUTES_15_CACHE -> QUARTER_CACHE

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23337/files
  - new: https://git.openjdk.org/jdk/pull/23337/files/3ec3c64c..2402d5c8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23337&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23337&range=01-02

  Stats: 4 lines in 1 file changed: 0 ins; 1 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/23337.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23337/head:pull/23337

PR: https://git.openjdk.org/jdk/pull/23337