[jdk11u-dev] RFR: 8306133: Open source few AWT Drag & Drop related tests

[Andrew Lu]

I backport this for parity with 11.0.21-oracle.

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Commit messages:
 - Backport ec5c7926f3cea68bf0d0ceb460a8383f5e4ea278

Changes: https://git.openjdk.org/jdk11u-dev/pull/2076/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2076&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306133
  Stats: 1062 lines in 5 files changed: 1062 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2076.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2076/head:pull/2076

PR: https://git.openjdk.org/jdk11u-dev/pull/2076