[jdk21u-dev] RFR: 8367237: Thread-Safety Usage Warning for java.text.Collator Classes

[Goetz Lindenmaier]

I backport this for parity with 21.0.10-oracle.

-------------

Commit messages:
 - backport 64155dfac068cf01bcab6adb401b360499f33a5f

Changes: https://git.openjdk.org/jdk21u-dev/pull/2351/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2351&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8367237
  Stats: 17 lines in 2 files changed: 10 ins; 4 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2351.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2351/head:pull/2351

PR: https://git.openjdk.org/jdk21u-dev/pull/2351