RFR: 8294589: MenuBarSkin: memory leak when changing skin [v21]

[Andy Goryachev]

> Fixed memory leak by using weak listeners and making sure to undo everything that has been done to MenuBar/Skin in dispose().
> 
> This PR depends on a new internal class ListenerHelper, a replacement for LambdaMultiplePropertyChangeListenerHandler.
> See https://github.com/openjdk/jfx/pull/908

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

  8294589: trying to avoid merge conflicts in the future

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Changes:
  - all: https://git.openjdk.org/jfx/pull/906/files
  - new: https://git.openjdk.org/jfx/pull/906/files/4434e5f7..b546a15b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=906&range=20
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=906&range=19-20

  Stats: 17 lines in 1 file changed: 17 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx/pull/906.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/906/head:pull/906

PR: https://git.openjdk.org/jfx/pull/906