RFR: 8306466: Open source more AWT Drag & Drop related tests

[Damon Nguyen]

This PR open sources a few more AWT DnD related tests

-------------

Commit messages:
 - Add dnd tests

Changes: https://git.openjdk.org/jdk/pull/13653/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13653&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306466
  Stats: 838 lines in 8 files changed: 838 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13653.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13653/head:pull/13653

PR: https://git.openjdk.org/jdk/pull/13653