[jdk17u-dev] RFR: 8306681: Open source more AWT DnD related tests

[Victor Rudometov]

Clean backport, new tests, low risk
Checked on macOS x64, linux x64, windows x64: tests pass

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Commit messages:
 - Backport 05af487a2d9b85b87d13ea23776d04e52c67bf49

Changes: https://git.openjdk.org/jdk17u-dev/pull/1365/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1365&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306681
  Stats: 544 lines in 7 files changed: 544 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1365.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1365/head:pull/1365

PR: https://git.openjdk.org/jdk17u-dev/pull/1365