Allow reimporting assets in background with no window focus

[passivestar]

Describe the project you are working on

An editor plugin that makes it possible to reload nodes in a running game after asset reimport, see this for more context:
#9519

Describe the problem or limitation you are having in your project

When changing a file externally (gltf in my case), editor won't reimport it until it gets focus. This is a problem because I'm relying on EditorFileSystem.resources_reimported signal to send the list of the reimported assets to the running game through an EditorDebuggerPlugin to reload them in-game

Would be nice if it also didn't flash the reimport progress popup on top of all of the other windows because in this workflow you'd only be interested in the 3d editor (blender) window and the running game window, editor showing the import progress popup on top of everything is just distracting

Also a related problem: for some reason after the asset reimport after godot window gets focus it opens a random script in the script editor (which is vscode in my case). I don't know if this is tracked anywhere

Describe the feature / enhancement and how it helps to overcome the problem or limitation

An editor setting that will allow the editor to reimport assets even when it doesn't have focus

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

If this enhancement will not be used often, can it be worked around with a few lines of script?

N/A

Is there a reason why this should be core and not an add-on in the asset library?

N/A

[MarioLiebisch]

I guess this was originally done to prevent any issues with files still open or only partially written (think of an editor like Blender only saving the model and then the material file or vice-versa).

Maybe there could be ab option to reimport changed files like "Once every x seconds" or "Only when focus is regained".

[Calinou]

Thanks for the proposal! Consolidating in #3252.