RFR: JDK-8286789: Test forceEarlyReturn002.java timed out

[Alex Menkov]

This is an attempt to fix suspicious code in the forceEarlyReturn002.java and un-problemlist it to see if the problem appear again.

The test fails in "virtual thread factory" mode with timeout for unclear reason after it finished testing and performs cleanup process (debugger sends debuggee a command to exit, but debuggee doesn't receive the command).
This is the only test which has this intermittent communication failures.
The test was problem-listed, I was not able to reproduce the issue with 1000+ runs.

Debuggee creates a thread which executes tight infinite loop in native code (in "virtual thread factory" mode it's pinned virtual thread).
The fix adds delays in the loop and adds new command to exit from native method after testing.

Testing: 100 runs in "virtual thread factory" mode on all Oracle supported platforms.

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Commit messages:
 - forceEarlyReturn002

Changes: https://git.openjdk.org/jdk/pull/15301/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15301&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286789
  Stats: 47 lines in 4 files changed: 34 ins; 8 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/15301.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15301/head:pull/15301

PR: https://git.openjdk.org/jdk/pull/15301