<i18n dev> RFR: 8269409: Post JEP 411 refactoring: core-libs with maximum covering > 10K

[Weijun Wang]

More refactoring to limit the scope of `@SuppressWarnings` annotations.

Sometimes I introduce new methods. Please feel free to suggest method names you like to use.

Note: this is copied from https://github.com/openjdk/jdk17/pull/152.

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Commit messages:
 - copy all code change from jdk17

Changes: https://git.openjdk.java.net/jdk/pull/4615/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4615&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269409
  Stats: 293 lines in 21 files changed: 165 ins; 64 del; 64 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4615.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4615/head:pull/4615

PR: https://git.openjdk.java.net/jdk/pull/4615