RFR: 8351187: Add JFR monitor notification event [v2]

[Aleksey Shipilev]

> We have `JavaMonitorWait` event, but no symmetric `JavaMonitorNotify` event. Notifications are important/interesting to track as well, for example to correlate the delay between notification and eventual wake up.
> 
> Providing this event would also replace one of of the RT counters that are going away in [JDK-8348829](https://bugs.openjdk.org/browse/JDK-8348829).
> 
> This counter is disabled by default to keep any potential impact low. We can consider flipping it to enabled by default later.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `jdk_jfr`

Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - Drop threshold to 0ms
 - Merge branch 'master' into JDK-8351187-jfr-monitor-notify
 - Disable by default
 - Fix

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23901/files
  - new: https://git.openjdk.org/jdk/pull/23901/files/792934ff..bae0c391

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23901&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23901&range=00-01

  Stats: 5245 lines in 131 files changed: 2978 ins; 1296 del; 971 mod
  Patch: https://git.openjdk.org/jdk/pull/23901.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23901/head:pull/23901

PR: https://git.openjdk.org/jdk/pull/23901