RFR: 8307308: Add serviceability_ttf_virtual group to exclude jvmti tests developed for virtual threads

[Leonid Mesnik]

Please review following trivial fix which add serviceability_ttf_virtual test group.
There are several directories with jvmti tests developed for testing virtual threads. It does't make sense to run them with virtual test thread factory. So the group serviceability_ttf_virtual is introduced to run all other svc test in this mode.

-------------

Commit messages:
 - 8307308: Add serviceability_ttf_virtual group to exclude jvmti tests developed for virtual threads

Changes: https://git.openjdk.org/jdk/pull/13782/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13782&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307308
  Stats: 7 lines in 1 file changed: 7 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13782.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13782/head:pull/13782

PR: https://git.openjdk.org/jdk/pull/13782