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

[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. The event wants to record it, touches the dead object and crashes. The fix is simple: since we cannot infer any useful information from the event, we just skip the event emit.

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`

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Commit messages:
 - Stress test
 - Blind fix

Changes: https://git.openjdk.org/jdk/pull/24121/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24121&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8352414
  Stats: 158 lines in 2 files changed: 157 ins; 0 del; 1 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