RFR: 8306133: Open source few AWT Drag & Drop related tests [v2]

[Damon Nguyen]

On Fri, 21 Apr 2023 23:09:32 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> There's no harm in doing that but I'm not sure its necessary for the dispose().
>
> it is fine to call dispose here on the main, but the frame possibly can be null here.

I have updated the tests to all dispose on the EDT just in case.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13591#discussion_r1176755562