[jdk21u-dev] RFR: 8370636: com/sun/jdi/TwoThreadsTest.java should wait for completion of all threads

[SendaoYan]

Hi all,

This pull request contains a backport of commit [d1860370](https://github.com/openjdk/jdk/commit/d1860370635e1c96a9b6c497861e5573c23dd281) from the [openjdk/jdk](https://git.openjdk.org/jdk) repository.

The commit being backported was authored by Leonid Mesnik on 28 Oct 2025 and was reviewed by Chris Plummer, SendaoYan and Serguei Spitsyn.

This backport PR fix the test bug which the new virtual thread missing join() and will exit immediately. Change has been verified locally on linux-x64.

Thanks!

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Commit messages:
 - Backport d1860370635e1c96a9b6c497861e5573c23dd281

Changes: https://git.openjdk.org/jdk21u-dev/pull/2423/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2423&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370636
  Stats: 8 lines in 1 file changed: 7 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2423.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2423/head:pull/2423

PR: https://git.openjdk.org/jdk21u-dev/pull/2423