RFR: 8373439: Deadlock between flight recorder & VMDeath

[Bara' Hasheesh]

A simple `PlatformRecorder.isInShutDown` check is added to `PlatformRecording.start` to prevent any new recording from start after the JVM initiates it's shutdown hooks  

A new test was added that fails without the change & passes with it 

I also ran `tier1`, `tier2` as well as `jdk_jfr` on Linux x86

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Commit messages:
 - exception message
 - Move shutdown check to PlatformRecorder.start & missing space
 - 8373439: Fix deadlock between recorder start & VMDeath hook

Changes: https://git.openjdk.org/jdk/pull/28767/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28767&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8373439
  Stats: 66 lines in 3 files changed: 64 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/28767.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28767/head:pull/28767

PR: https://git.openjdk.org/jdk/pull/28767