[jdk17] RFR: 8268702: JFR diagnostic commands lack argument descriptors when viewed using Platform MBean Server

[Markus Grönlund]

Greetings,

this changeset restores the diagnostic command argument descriptors that got lost as part of [JDK-8265271](https://bugs.openjdk.java.net/browse/JDK-8265271) .

Testing: jdk_jfr, manual verification

Thanks
Markus

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Commit messages:
 - 8268702: JFR diagnostic commands lack argument descriptors when viewed using Platform MBean Server

Changes: https://git.openjdk.java.net/jdk17/pull/57/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=57&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268702
  Stats: 105 lines in 3 files changed: 95 ins; 4 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/57.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/57/head:pull/57

PR: https://git.openjdk.java.net/jdk17/pull/57