RFR: 8295500: AccordionSkin: memory leak when changing skin

[Andy Goryachev]

as determined by SkinMemoryLeakTest (remove line 164) and a leak tester
https://github.com/andy-goryachev-oracle/Test/blob/main/src/goryachev/apps/LeakTest.java

Make sure to configure the current test in LeakTest:
protected final Type WE_ARE_TESTING = Type.ACCORDION;


caused by:
- adding and not removing listeners

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Commit messages:
 - 8295500: cleanup
 - Merge remote-tracking branch 'origin/master' into 8295500.accordion.skin
 - Merge branch '8294809.listener.helper' into 8295500.accordion.skin
 - 8294809: generics
 - Merge branch '8294809.listener.helper' into 8295500.accordion.skin
 - 8294809: is alive
 - Merge branch '8294809.listener.helper' into 8295500.accordion.skin
 - Revert "8294809: removed weak listeners support"
 - 8295500: cleanup
 - 8295500: cleanup
 - ... and 16 more: https://git.openjdk.org/jfx/compare/3376228a...513aa910

Changes: https://git.openjdk.org/jfx/pull/920/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=920&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295500
  Stats: 32 lines in 2 files changed: 16 ins; 7 del; 9 mod
  Patch: https://git.openjdk.org/jfx/pull/920.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/920/head:pull/920

PR: https://git.openjdk.org/jfx/pull/920