RFR: 8262271: SA: Add new stress test that tests getting the stack trace of an active thread [v2]

[Chris Plummer]

> This a new test that runs jstack on a process that is busy doing things. It runs jstack 4 times as the process is starting up.

Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:

  Use waitFor() instead of destroyForcibly().

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2720/files
  - new: https://git.openjdk.java.net/jdk/pull/2720/files/e9bfe2be..6689e8ac

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2720&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2720&range=00-01

  Stats: 8 lines in 1 file changed: 1 ins; 4 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2720.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2720/head:pull/2720

PR: https://git.openjdk.java.net/jdk/pull/2720