Do not run the InfoTextSwingWorker on the EDT thread

[kwvanderlinde]

Identify the Bug or Feature request

Fixes #4801

Description of the Change

This changes the data gathering task for Gather Debug Information... to run on a background thread rather than the EDT thread. The dialog as a result now shows the text "Gathering information, please wait..." until the dialog is populated, rather than being blank. The dialog also no longer hangs indefinitely.

The reason we previously got away with running that task on the EDT thread is that SwingWorker would always run the done() method after the internal FutureTask<> completes, so the get() method would have a result to return. But since Java 21, it runs done() as part of the FutureTask<> callback if running on the EDT thread, i.e., it runs done() before the task completes. The get() call therefore blocks as it has no result yet, and the task is blocked from completing and providing those results.

I audited the rest of our SwingWorker tasks, but they are all run via .execute() and thus are safe from this issue. Only one task (RenderPathWorker) is run in a dfiferent manner, but it is on its own non-EDT executor. One unnecessary usage of that worker was found and removed though.

Possible Drawbacks

None

Documentation Notes

N/A

Release Notes

• Fixed a bug where Gather Debug Information... would permanently hang MapTool.

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This change is 

[kwvanderlinde]

Targetting the 1.15 release with this one so bugs can be properly reported for that version.