RFR: 8367237: Thread-Safety Usage Warning for java.text.Collator Classes [v2]

[Justin Lu]

> Please review this PR which is a documentation change to make apparent the recommended approach for using Collator & RuleBasedCollator in a multi threaded environment via an implNote. The original issue and CSR have additional context.

Justin Lu has updated the pull request incrementally with one additional commit since the last revision:

  Doc updates reflecting Naoto's comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27233/files
  - new: https://git.openjdk.org/jdk/pull/27233/files/d15faad4..5fab9652

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27233&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27233&range=00-01

  Stats: 8 lines in 2 files changed: 1 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/27233.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27233/head:pull/27233

PR: https://git.openjdk.org/jdk/pull/27233