Map: initialize screen width and height on SetupCommon

[aidatorajiro]

fixes #3327.
(i don't know how this patch interferes with #3293, but Init() is called only after reset, so not a very destructing change i guess)

[Ghabry]

I think I deleted this because I assumed Setup is always called 🤔. Have to check the control flow 😅. Thanks

[Ghabry]

@aidatorajiro I checked this now and Setup is indeed not called when loading from a save (only SetupFromSave is).

Can you try deleting the

screen_width = (Player::screen_width / 16.0) * SCREEN_TILE_SIZE;
screen_height = (Player::screen_height / 16.0) * SCREEN_TILE_SIZE;

from Init and Setup and instead add these lines at the beginning of SetupCommon.

[Ghabry]

Squashed all commits into one as the intermediate commits were unnecessary here. Otherwise no changes from my side.