RFR: 8305608: Change VMConnection to use "test.class.path"instead of "test.classes"

[Leonid Mesnik]

Currently, VMConnection run debugee using "test.classes" as a classpath. It cause test failures when virtual thread factory (wrapper) is enabled and test is not located the same directory as TestScaffold.

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Commit messages:
 - more tests are added
 - updated vmconnection

Changes: https://git.openjdk.org/jdk/pull/13339/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13339&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305608
  Stats: 17 lines in 2 files changed: 3 ins; 12 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/13339.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13339/head:pull/13339

PR: https://git.openjdk.org/jdk/pull/13339