RFR: 8315594: Open source few headless Swing misc tests

[Prasanta Sadhukhan]

Few closed swing tests are open sourced

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Commit messages:
 - 8315594:Open source few headless Swing misc tests

Changes: https://git.openjdk.org/jdk/pull/15577/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15577&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315594
  Stats: 256 lines in 4 files changed: 256 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/15577.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15577/head:pull/15577

PR: https://git.openjdk.org/jdk/pull/15577