RFR: 8332738: Debug agent can deadlock on callbackLock when using StackFrame.PopFrames

[Chris Plummer]

Fix deadlock with debug agent callbackLock. Details in first comment.

Tested by running all jdi, jdwp, and jdb tests with and without virtual threads about 40 times. The testing was initially done with my hack to force the self suspend (see the first comment in the CR), and then I did final testing without it. I also did final testing with all tier5 svc tests.

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Commit messages:
 - Fix deadlock with callbackLock.

Changes: https://git.openjdk.org/jdk/pull/20282/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20282&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8332738
  Stats: 44 lines in 5 files changed: 29 ins; 3 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/20282.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20282/head:pull/20282

PR: https://git.openjdk.org/jdk/pull/20282