RFR: 8370846: Support execution of mlvm testing with test thread factory

[Leonid Mesnik]

The MainWrapper used test thread factory has generated lambda method. So the AbsentInformationException is expected.  The actual source path is not checked.

Tested by run mlvm tests with and without test thread factory.

Also
jdk/test/lib/thread/TestThreadFactory.java
updated to provide TestThreadFactory. isTestThreadFactorySet() 
that could be used by tests instead of checking property "test.thread.factory" directly.

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Commit messages:
 - fixed checks
 - 8370846: Support execution of mlvm testing with test thread factory

Changes: https://git.openjdk.org/jdk/pull/28028/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28028&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8370846
  Stats: 37 lines in 2 files changed: 32 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/28028.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28028/head:pull/28028

PR: https://git.openjdk.org/jdk/pull/28028