RFR: 8349255: TitledPane: exception initializing in a background thread

[Andy Goryachev]

## Root Cause

Animation was started in the background thread, causing concurrent access.

## Solution

Disable animation if not the fx app thread.

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

Commit messages:
 - the fix
 - Merge branch 'master' into 8349255.thread.safe.titled.pane
 - Merge branch 'master' into 8349255.thread.safe.titled.pane
 - get parent
 - Merge branch '8348423.node.thread.safety' into 8347392.thread.safe.utils
 - review comments
 - Merge remote-tracking branch 'origin/master' into 8348423.node.thread.safety
 - Merge branch '8348423.node.thread.safety' into 8347392.thread.safe.utils
 - more jitter
 - disabled titled pane test
 - ... and 15 more: https://git.openjdk.org/jfx/compare/1e691573...8426f326

Changes: https://git.openjdk.org/jfx/pull/1707/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1707&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349255
  Stats: 28 lines in 3 files changed: 11 ins; 10 del; 7 mod
  Patch: https://git.openjdk.org/jfx/pull/1707.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1707/head:pull/1707

PR: https://git.openjdk.org/jfx/pull/1707