RFR: 8295531: ComboBoxBaseSkin: memory leak when changing skin [v4]

[Andy Goryachev]

> as determined by SkinMemoryLeakTest (remove line 166) and a leak tester
> https://github.com/andy-goryachev-oracle/Test/blob/main/src/goryachev/apps/LeakTest.java
> 
> Affected skins:
> - ColorPicker
> - DatePicker
> - ComboBox
> 
> caused by:
> - out-of-order modification of the control property (skin.install)
> - adding skin nodes and not removing them in dispose()
> - adding listeners and not removing them in dispose()
> 
> NOTE: the fix will require not only ListenerHelper [JDK-8294809](https://bugs.openjdk.org/browse/JDK-8294809) but also Skin.install() [JDK-8290844](https://bugs.openjdk.org/browse/JDK-8290844) changes.

Andy Goryachev has updated the pull request incrementally with one additional commit since the last revision:

  8295531: trying to avoid merge conflicts in the future

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

Changes:
  - all: https://git.openjdk.org/jfx/pull/922/files
  - new: https://git.openjdk.org/jfx/pull/922/files/735b2d53..968b08cb

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=922&range=03
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=922&range=02-03

  Stats: 13 lines in 1 file changed: 13 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/922.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/922/head:pull/922

PR: https://git.openjdk.org/jfx/pull/922