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. ------------- Commit messages: - Fix TreeTableView graphic property issue Changes: https://git.openjdk.org/jfx/pull/1172/files Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1172&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8285700 Stats: 32 lines in 2 files changed: 31 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
