RFR: 8285700: [TreeTableView] graphic property of TreeItem is still visible after collapsing tree [v4]

[Karthik P K]

> In `TreeTableRowSkin`, graphic was not updated along with tree item update.
> 
> Made changes to update graphics of TreeTableView row in `updateTreeItem()` method.
> 
> Added options in monkey tester to add graphics and subnodes to `TreeTableView` rows.

Karthik P K has updated the pull request incrementally with one additional commit since the last revision:

  Review comments

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1172/files
  - new: https://git.openjdk.org/jfx/pull/1172/files/78a91a57..369035c1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1172&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1172&range=02-03

  Stats: 5 lines in 1 file changed: 0 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1172.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1172/head:pull/1172

PR: https://git.openjdk.org/jfx/pull/1172