RFR: 8348423: [TestBug] stress test Nodes initialization from a background thread

[Andy Goryachev]

Created a test that validates various Nodes can be initialized in a background thread.

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Commit messages:
 - cleanup
 - pagination
 - thread count
 - all controls
 - more tests
 - initial test

Changes: https://git.openjdk.org/jfx/pull/1690/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1690&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348423
  Stats: 1224 lines in 3 files changed: 1097 ins; 125 del; 2 mod
  Patch: https://git.openjdk.org/jfx/pull/1690.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1690/head:pull/1690

PR: https://git.openjdk.org/jfx/pull/1690