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

[Harshitha Onkar]

On Tue, 15 Apr 2025 19:37:47 GMT, Damon Nguyen <dnguyen at openjdk.org> wrote:

>> 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

Marked as reviewed by honkar (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/24559#pullrequestreview-2770080511