[jdk11u-dev] RFR: 8306941: Open source several datatransfer and dnd AWT tests

[Amos Shi]

Backport of [JDK-8306941](https://bugs.openjdk.org/browse/JDK-8306941)

Testing
- Local: Test passed
  - `MimeFormatsTest.java`: Test results: no tests selected
  - `RemoveFlavorListenerTest.java`: Test results: passed: 1
  - `AutoscrollStopTest.java`: Test results: passed: 1
  - `ButtonReleaseTest.java`: Test results: passed: 1
- Pipeline: 
- Testing Machine:

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Commit messages:
 - Backport 3d3eaed9133dbe728ca8e00a626d33f7e35ba9ff

Changes: https://git.openjdk.org/jdk11u-dev/pull/2566/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2566&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306941
  Stats: 831 lines in 4 files changed: 831 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2566.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2566/head:pull/2566

PR: https://git.openjdk.org/jdk11u-dev/pull/2566