[jdk21u-dev] RFR: 8315594: Open source few headless Swing misc tests

[Andrew Lu]

I backport this for parity with 21.0.3-oracle.

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Commit messages:
 - Backport 806ef0897b42c8f3cb3b4d7bd904af9ed18a543e

Changes: https://git.openjdk.org/jdk21u-dev/pull/174/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=174&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/jdk21u-dev/pull/174.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/174/head:pull/174

PR: https://git.openjdk.org/jdk21u-dev/pull/174