Fix: Fix undo/redo while action menu is open

[phoenixeliot]

This applies a minimal fix for #6267 and #6269.

I think it's a good change on its own, but there are potentially other changes to make to fully fix buggy behavior around how the editor never saves while the action menu is open; see #6267 (comment) for more on that.

Changes in this PR:

• Adds automated test; I had to add a data class to the modal to be able to check for it with the tests. (The data attribute code is the same as in Feat: Press escape to close action menu #6270)
• Clear the current editor action before performing an undo or redo. For undo, this allows the editor to save the way it normally tries to before undoing (so that the changes are redoable). For redo, it's a little unclear to me on why this causes redo history to be correct (if you make an edit in a [[]] it should replace the redo stack), but it does, and causes correct behavior.

[phoenixeliot]

I'm going to mark this ready for review in case y'all think it's mergable, though it does still feel like it's pending some discussion at #6267 (comment) as mentioned above.