RFR: 8271931: Make AbortVMOnVMOperationTimeout more resilient to OS scheduling

[Albert Mingkun Yang]

Perform VM-op timeout also on the VM thread. If a VM-op is stuck, the existing watcher-thread based machinery will kick in and detect it.

Test: tier1

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Commit messages:
 - review
 - vmthread-timeout

Changes: https://git.openjdk.java.net/jdk/pull/5016/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5016&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271931
  Stats: 14 lines in 2 files changed: 9 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5016.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5016/head:pull/5016

PR: https://git.openjdk.java.net/jdk/pull/5016