[jdk21u-dev] RFR: 8353748: Open source several swing tests batch6

[Satyen Subramaniam]

Backporting JDK-8353748: Open source several swing tests batch6. Adds six tests for nodes in UI file system tree. Ran GHA Sanity Checks, local Tier 1 and 2, and new tests directly. Patch is clean. Backporting for parity with Oracle.

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Commit messages:
 - Backport 38f9b3a9738de7896d840fc114a76ced3b77c269

Changes: https://git.openjdk.org/jdk21u-dev/pull/2119/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2119&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353748
  Stats: 501 lines in 6 files changed: 501 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2119.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2119/head:pull/2119

PR: https://git.openjdk.org/jdk21u-dev/pull/2119