RFR: 8285700: [TreeTableView] graphic property of TreeItem is still visible after collapsing tree [v3]

[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/8d8fdae8..78a91a57

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1172&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1172&range=01-02

  Stats: 4 lines in 1 file changed: 3 ins; 0 del; 1 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