RFR: 8351187: Add JFR monitor notification event

[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`

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Commit messages:
 - Disable by default
 - Fix

Changes: https://git.openjdk.org/jdk/pull/23901/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23901&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8351187
  Stats: 161 lines in 7 files changed: 155 ins; 0 del; 6 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