[Feat] GUI Location Download window should not be modal

[mlennert]

Is your feature request related to a problem? Please describe.

When I launch a location download from within the GUI, the "Location Download" window is modal and keeps me from interacting with the rest of the GUI. I can launch a terminal and work there, but downloading a location should not keep me from working on other data in by GISDBASE.
This is especially annoying on a day when the download is extremely slow (around 100 KB/s).

Describe the solution you'd like

Downloads should happen in the background, with a possible notification when the download is finished.

Additional context

GRASS 8.3.1 Apple ARM
Mac OSX, Sonoma 14.1.1 (don't have the opportunity to test on a different system at the moment)

The only reactive part of the GUI is the menu, but all module menu entries are deactivated as can be seen in the screenshot: