Integrated: Merge jfx18

[Kevin Rushforth]

Merge ...Merge `jfx18` into `master`.

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Commit messages:
 - Merge jfx18
 - 8244234: MenuButton: NPE on removing from scene with open popup
 - 8279615: Change JavaFX release version to 19

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.java.net/jfx/pull/719/files
  Stats: 136 lines in 5 files changed: 126 ins; 1 del; 9 mod
  Patch: https://git.openjdk.java.net/jfx/pull/719.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/719/head:pull/719

PR: https://git.openjdk.java.net/jfx/pull/719