RFR: 8365635: Add MOUSE_DRAG_DONE event type

[Nir Lisker]

Adds `MOUSE_DRAG_DONE` event type to `MouseDragEvent` and appropriate handlers.

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/jfx/pull/1873/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1873&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365635
  Stats: 98 lines in 5 files changed: 90 ins; 3 del; 5 mod
  Patch: https://git.openjdk.org/jfx/pull/1873.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1873/head:pull/1873

PR: https://git.openjdk.org/jfx/pull/1873