Remove some UI calls from overmap creation

Fixes #7505

The freezing is cause by the creation of the other overmap. Nothing can be done about this, the overmap has to be created at some point. It used to be created when you open the map screen and scroll around (it would create overmaps even if you could not see anything of them). Now it only creates them when they are actually needed.

The minimap bug is fixed by this PR.

`erase` and `clear` operate on the main window, `move` is most likely the function defined in src/catacurse.h / the one defined in a ncurses header.