RFR: 8306871: Open source more AWT Drag & Drop tests

[Damon Nguyen]

This PR open sources more AWT DnD & Event related tests

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Commit messages:
 - Initial test add

Changes: https://git.openjdk.org/jdk/pull/13725/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13725&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306871
  Stats: 1916 lines in 6 files changed: 1916 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13725.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13725/head:pull/13725

PR: https://git.openjdk.org/jdk/pull/13725