RFR: 8349750: [TestBug] NodeInitializationStressTest: remaining Nodes

[Andy Goryachev]

## Added Missing Controls

ButtonBar
ProgressIndicator
Separator
Slider,

## Added Node Classes

AnchorPane
AmbientLight
Arc
BorderPane
Box
Circle
CubicCurve
Cylinder
DialogPane
DirectionalLight
Ellipse
FlowPane
GridPane
Group
HBox
ImageView
Line
MediaView
MeshView
Pane
ParallelCamera
Path
PerspectiveCamera
PointLight
Polygon
Polyline
QuadCurve
Rectangle
Region
Sphere
StackPane
SVGPath
TilePane
VBox


## Miscellaneous

- minor improvements
- remove tests that execute show() in non-fx threads per [JDK-8350048](https://bugs.openjdk.org/browse/JDK-8350048)



## Not Included Due to Threading Limitations

HTMLEditor
MenuBar
SwingNode
WebView

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

Commit messages:
 - cleanup
 - images
 - Merge remote-tracking branch 'origin/master' into 8349750.stress.2
 - media
 - Merge remote-tracking branch 'origin/master' into 8349750.stress.2
 - 3d
 - shapes
 - show()
 - Merge remote-tracking branch 'origin/master' into 8349750.stress.2
 - panes
 - ... and 2 more: https://git.openjdk.org/jfx/compare/065548d0...6d4e99f7

Changes: https://git.openjdk.org/jfx/pull/1713/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1713&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349750
  Stats: 868 lines in 2 files changed: 829 ins; 13 del; 26 mod
  Patch: https://git.openjdk.org/jfx/pull/1713.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1713/head:pull/1713

PR: https://git.openjdk.org/jfx/pull/1713