RFR: Debugger changes to support JVMTI now returning JVMTI_ERROR_UNSUPPORTED_OPERATION for Thread.stop() of a virtual thread.

[Chris Plummer]

Debugger changes to support JVMTI now returning JVMTI_ERROR_UNSUPPORTED_OPERATION for Thread.stop() of a virtual thread.

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Commit messages:
 - Update JDI spec for ThreadReference.stop().
 - Undo timeout changes.
 - Debugger changes to support JVMTI now returning JVMTI_ERROR_UNSUPPORTED_OPERATION for Thread.stop() of a virtual thread.

Changes: https://git.openjdk.java.net/loom/pull/146/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=146&range=00
  Stats: 18 lines in 7 files changed: 8 ins; 2 del; 8 mod
  Patch: https://git.openjdk.java.net/loom/pull/146.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/146/head:pull/146

PR: https://git.openjdk.java.net/loom/pull/146