[jdk21u-dev] RFR: 8315731: Open source several Swing Text related tests

[Jonathan Dowland]

For Oracle parity. Cherry picks clean. Test only. Introduces 5 newly-open-sourced Swing tests which all pass.

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Commit messages:
 - Backport d475f61fd52b7d379260811b32d3815786858411

Changes: https://git.openjdk.org/jdk21u-dev/pull/124/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=124&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315731
  Stats: 468 lines in 5 files changed: 468 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/124.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/124/head:pull/124

PR: https://git.openjdk.org/jdk21u-dev/pull/124