[jdk11u-dev] RFR: 8306871: Open source more AWT Drag & Drop tests

[Andrew Lu]

I backport this for parity with 11.0.23-oracle.

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Commit messages:
 - Backport b5a48277ab5b42c4b13db7ddb5418a17ada512ec

Changes: https://git.openjdk.org/jdk11u-dev/pull/2447/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2447&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306871
  Stats: 1915 lines in 6 files changed: 1915 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2447.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2447/head:pull/2447

PR: https://git.openjdk.org/jdk11u-dev/pull/2447