[jdk21u-dev] RFR: 8368328: CompactNumberFormat.clone does not produce independent instances

[Roland Mesde]

Backporting JDK-8368328: CompactNumberFormat.clone does not produce independent instances. Fixes clone method logic and adds a new test. Ran GHA Sanity Checks (passed) and new test (passed). Patch is clean.

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

Commit messages:
 - Backport bdf6853cfdd24176bdddb59b6d7bb85036b94c57

Changes: https://git.openjdk.org/jdk21u-dev/pull/2462/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2462&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368328
  Stats: 114 lines in 2 files changed: 106 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2462.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2462/head:pull/2462

PR: https://git.openjdk.org/jdk21u-dev/pull/2462