RFR: 8307538: Memory leak in TreeTableView when calling refresh

[Andy Goryachev]

Fixed a memory leak in TreeTableView by using WeakInvalidationListener (which is the right approach in this particular situation) - the leak is specific to TreeTableRowSkin.

Added a unit test.

Added Refresh buttons and Skin menu to the Monkey Tester (will expand these to other controls as a part next MT update).

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Commit messages:
 - whitespace
 - updated test
 - variable tree cell fix
 - fixed size selector
 - list view page
 - fix and test
 - skin menu
 - refresh button

Changes: https://git.openjdk.org/jfx/pull/1129/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1129&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307538
  Stats: 202 lines in 7 files changed: 160 ins; 15 del; 27 mod
  Patch: https://git.openjdk.org/jfx/pull/1129.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1129/head:pull/1129

PR: https://git.openjdk.org/jfx/pull/1129