RFR: 8354695: Open source several swing tests batch7 [v5]

[Damon Nguyen]

> Open-sourcing and standardizing several swing tests (JScrollPane & JRootPane)

Damon Nguyen has updated the pull request incrementally with one additional commit since the last revision:

  Add to EDT

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24758/files
  - new: https://git.openjdk.org/jdk/pull/24758/files/7ee15af3..920006e3

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24758&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24758&range=03-04

  Stats: 68 lines in 1 file changed: 29 ins; 2 del; 37 mod
  Patch: https://git.openjdk.org/jdk/pull/24758.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24758/head:pull/24758

PR: https://git.openjdk.org/jdk/pull/24758