RFR: 8365615: Improve JMenuBar/RightLeftOrientation.java

[Prasanta Sadhukhan]

On Fri, 15 Aug 2025 16:46:16 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> Position the two frames with menu bars in left-to-right and right-to-left orientations below the frame that allows changing the look and feel.
> 
> Additionally, amend the instructions and refactor the code, show an error message to the tester if setting L&F fails.

Marked as reviewed by psadhukhan (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26803#pullrequestreview-3143297266