RFR: 8295500: AccordionSkin: memory leak when changing skin [v2]

[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

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 27 commits:

 - Merge remote-tracking branch 'origin/master' into 8295500.accordion.skin
 - 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"
   
   This reverts commit 2df4a85db638d76cacaf6c54ba669cdb3dd91a18.
 - 8295500: cleanup
 - ... and 17 more: https://git.openjdk.org/jfx/compare/0a785ae0...218c6ea9

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Changes: https://git.openjdk.org/jfx/pull/920/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=920&range=01
  Stats: 31 lines in 2 files changed: 16 ins; 6 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