RFR: 8301492: Modernize equals() method of ResourceBundle.CacheKey and Bundles.CacheKey [v5]

[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 `ResourceBundle.CacheKey.equals()` and `Bundles.CacheKey.equals()` are quire outdated.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 incrementally with one additional commit since the last revision:

  8301492: Revert

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12328/files
  - new: https://git.openjdk.org/jdk/pull/12328/files/e304cfe7..28f0e270

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12328&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12328&range=03-04

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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