[jfx21u] RFR: 8319779: SystemMenu: memory leak due to listener never being removed

[Johan Vos]

almost clean backport of 8319779: SystemMenu: memory leak due to listener never being removed
Didn't apply clean because the imports where shuffled.

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Commit messages:
 - Backport 25ac6fed22d0f49d01c831aaa48049c34899fe96

Changes: https://git.openjdk.org/jfx21u/pull/66/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx21u&pr=66&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319779
  Stats: 667 lines in 5 files changed: 462 ins; 196 del; 9 mod
  Patch: https://git.openjdk.org/jfx21u/pull/66.diff
  Fetch: git fetch https://git.openjdk.org/jfx21u.git pull/66/head:pull/66

PR: https://git.openjdk.org/jfx21u/pull/66