RFR: 8295426: MenuButtonSkin: memory leak when changing skin [v2]

[Andy Goryachev]

> as determined by SkinMemoryLeakTest (remove line 170) and a leak tester
> https://github.com/andy-goryachev-oracle/Test/blob/main/src/goryachev/apps/LeakTest.java
> 
> Also applies to SplitMenuButton, since they share the same base class MenuButtonSkinBase.
> 
> Make sure to configure the current test in LeakTest:
> protected final Type WE_ARE_TESTING = Type.MENU_BUTTON; // or SPLIT_MENU_BUTTON
> 
> In addition, there seems to be another failure scenario when simply replacing the skin - no menu is shown upon a click. To reproduce, launch LeakTest and click once on the [Replace Skin] button. Second click restores the function.
> 
> caused by:
> - adding and not removing EventHandlers
> - setting and not clearing onAction handlers
> - incorrect logic in setting mousePressed/mouse/Released handlers

Andy Goryachev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 37 commits:

 - Merge remote-tracking branch 'origin/master' into
   8295426.menu.button.skin
 - Merge remote-tracking branch 'origin/master' into
   8295426.menu.button.skin
 - 8295426: listener helper update
 - Merge remote-tracking branch 'origin/8294809.listener.helper' into 8295426.menu.button.skin
 - 8294809: review comments
 - Merge remote-tracking branch 'origin/master' into 8294809.listener.helper
 - 8294809: whitespace
 - 8294809: no public api
 - 8294809: map change listener
 - Merge remote-tracking branch 'origin/master' into 8294809.listener.helper
 - ... and 27 more: https://git.openjdk.org/jfx/compare/0a785ae0...800d3f1e

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Changes: https://git.openjdk.org/jfx/pull/919/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=919&range=01
  Stats: 175 lines in 4 files changed: 109 ins; 32 del; 34 mod
  Patch: https://git.openjdk.org/jfx/pull/919.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/919/head:pull/919

PR: https://git.openjdk.org/jfx/pull/919