RFR: 8288289: Preview APIs in jdk.jdi, jdk.management, and jdk.jfr should be reflective preview APIs

[Alan Bateman]

A number of the preview APIs added by JEP 425 exist to expose and support the virtual threads preview feature. Some of these APIs should be changed to be reflective preview APIs (see JEP 12). This will allow debuggers and other tooling to get a jump on  virtual threads without opting in themselves.

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Commit messages:
 - HotSpotDiagnosticMXBean.dumpThreads should be reflective too
 - Merge
 - Initial commit

Changes: https://git.openjdk.org/jdk19/pull/13/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk19&pr=13&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8288289
  Stats: 6 lines in 5 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk19/pull/13.diff
  Fetch: git fetch https://git.openjdk.org/jdk19 pull/13/head:pull/13

PR: https://git.openjdk.org/jdk19/pull/13