RFR: 8037914: Add JFR event for string deduplication [v3]

[Francesco Andreuzzi]

> 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).

Francesco Andreuzzi has updated the pull request incrementally with two additional commits since the last revision:

 - disable
 - revert

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28015/files
  - new: https://git.openjdk.org/jdk/pull/28015/files/bff0fd30..c3c9a8db

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28015&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28015&range=01-02

  Stats: 3 lines in 2 files changed: 0 ins; 2 del; 1 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