RFR: 8307538: Memory leak in TreeTableView when calling refresh [v3]

[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).

Andy Goryachev has updated the pull request incrementally with two additional commits since the last revision:

 - back to register listener
 - weak lambdas are getting collected

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/1129/files
  - new: https://git.openjdk.org/jfx/pull/1129/files/2b1ae8b7..4b9563cf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1129&range=02
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1129&range=01-02

  Stats: 43 lines in 2 files changed: 18 ins; 5 del; 20 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