RFR: 8334759: gc/g1/TestMixedGCLiveThreshold.java fails on Windows with JTREG_TEST_THREAD_FACTORY=Virtual due to extra memory allocation

[Thomas Schatzl]

Hi all,

  please review this change that "fixes" the `TestMixedGCLiveThreshold.java` test by requiring the thread factory used for these tests to not use virtual threads instead of platform threads.

That adds some additional memory consumption, and since the test is about testing G1 reaction due to particular known memory consumption, it can fail.

The fix is to add the appropriate `@requires` tag that has been introduced in jtreg 7.5.1 (which is current default/requirement for builds, https://bugs.openjdk.org/browse/JDK-8334759).

Testing: verified that the test is not run if the virtual thread test thread factory is used.

Thanks,
  Thomas

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Commit messages:
 - 8334759

Changes: https://git.openjdk.org/jdk/pull/25486/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25486&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8334759
  Stats: 8 lines in 2 files changed: 3 ins; 5 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25486.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25486/head:pull/25486

PR: https://git.openjdk.org/jdk/pull/25486