RFR: 8301492: Modernize equals() method of ResourceBundle.CacheKey and Bundles.CacheKey [v4]

[Sergey Tsypanov]

> `ResourceBundle.CacheKey.equals()` and `Bundles.CacheKey.equals()` are quire outdated. This simple clean-up modernizes them.

Sergey Tsypanov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:

 - 8301492: Revert
 - Merge branch 'master' into bundles
 - Restore logic
 - Fix logic
 - Copyright year update
 - Modernize Bubldes.equals()

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12328/files
  - new: https://git.openjdk.org/jdk/pull/12328/files/2b07e47e..e304cfe7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12328&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12328&range=02-03

  Stats: 1043296 lines in 10517 files changed: 730181 ins; 218415 del; 94700 mod
  Patch: https://git.openjdk.org/jdk/pull/12328.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/12328/head:pull/12328

PR: https://git.openjdk.org/jdk/pull/12328