RFR: 8273379 - GTK3 stops sending key events during drag and drop

Tue Dec 27 13:26:01 UTC 2022

This PR fixes 8273379.

I reverted back to use GDK (from [8225571](https://bugs.openjdk.org/browse/JDK-8225571)) to handle the events. 

It may fix [8280383](https://bugs.openjdk.org/browse/JDK-8280383).

There's also some cleaup.

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Commit messages:
 - 8373379 - Fix DND keys
 - 8373379 - Fix DND keys
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - Merge branch 'openjdk:master' into master
 - ... and 18 more: https://git.openjdk.org/jfx/compare/a35c3bf7...6f97561a

Changes: https://git.openjdk.org/jfx/pull/986/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=986&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8273379
  Stats: 971 lines in 8 files changed: 508 ins; 276 del; 187 mod
  Patch: https://git.openjdk.org/jfx/pull/986.diff
  Fetch: git fetch https://git.openjdk.org/jfx pull/986/head:pull/986

PR: https://git.openjdk.org/jfx/pull/986