RFR: 8352414: JFR: JavaMonitorDeflateEvent crashes when deflated monitor object is dead [v2]

[Aleksey Shipilev]

> Little regression crept in with [JDK-8351142](https://bugs.openjdk.org/browse/JDK-8351142): on the deflation path, object associated with monitor can be already dead. 
> 
> A new stress test fails within seconds without a fix. It also covers other monitor events, so we have extra coverage there as well.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, new stress test now passes
>  - [x] Linux x86_64 server fastdebug, `jdk_jfr`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Emit the event anyway

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/24121/files
  - new: https://git.openjdk.org/jdk/pull/24121/files/2b1d1b14..862a0176

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24121&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24121&range=00-01

  Stats: 22 lines in 3 files changed: 12 ins; 3 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/24121.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24121/head:pull/24121

PR: https://git.openjdk.org/jdk/pull/24121