[jdk21u-dev] RFR: 8316056: Open source several Swing JTree tests

[Goetz Lindenmaier]

I backport this for parity with 21.0.7-oracle

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Commit messages:
 - Backport 5f6cee86ef765677b0b9dc3662f4f20b636732bc

Changes: https://git.openjdk.org/jdk21u-dev/pull/1272/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1272&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316056
  Stats: 347 lines in 5 files changed: 347 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1272.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1272/head:pull/1272

PR: https://git.openjdk.org/jdk21u-dev/pull/1272