[jdk21u-dev] RFR: 8315876: Open source several Swing CSS related tests

[Goetz Lindenmaier]

I backport this for parity with 21.0.8-oracle

-------------

Commit messages:
 - Backport 833a82872c0b2517c7f4ae5d512cff3a428a071c

Changes: https://git.openjdk.org/jdk21u-dev/pull/1459/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1459&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315876
  Stats: 443 lines in 5 files changed: 443 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1459.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1459/head:pull/1459

PR: https://git.openjdk.org/jdk21u-dev/pull/1459