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