RFR: 8352908: Open source several swing tests batch1 [v2]

[Damon Nguyen]

> Open-sourcing and standardizing several tests (JSplitPane JApplet JToolBar)

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

  Update to setPreferredSize

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Changes:
  - all: https://git.openjdk.org/jdk/pull/24559/files
  - new: https://git.openjdk.org/jdk/pull/24559/files/81cdcd45..87a4df05

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=24559&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=24559&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/24559.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24559/head:pull/24559

PR: https://git.openjdk.org/jdk/pull/24559