RFR: 8285196: Deadlock reporting prints carrier thread when virtual thread is in deadlock cycle

[Ron Pressler]

Do not detect deadlock cycles, be it for monitors only or j.u.c `OwnableSynchronizer`s, when virtual threads are involved in the cycle.

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Commit messages:
 - Skip carriers in deadlock detection

Changes: https://git.openjdk.java.net/loom/pull/173/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=173&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285196
  Stats: 28 lines in 2 files changed: 9 ins; 14 del; 5 mod
  Patch: https://git.openjdk.java.net/loom/pull/173.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/173/head:pull/173

PR: https://git.openjdk.java.net/loom/pull/173