RFR: 8037914: Add JFR event for string deduplication

Tue Oct 28 10:21:24 UTC 2025

In this PR I introduce two new JFR events:
- `jdk.StringDeduplicationStatistics`
- `jdk.StringDeduplicationTimes`

The events are emitted every time a deduplication cycle happens, and they contain information about that cycle only.

Passes tier1 and tier2 (fastdebug).

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Commit messages:
 - trailing
 - thr
 - fix
 - revert
 - test
 - implement

Changes: https://git.openjdk.org/jdk/pull/28015/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28015&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8037914
  Stats: 306 lines in 9 files changed: 289 ins; 10 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/28015.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28015/head:pull/28015

PR: https://git.openjdk.org/jdk/pull/28015