Toggle to Only Draw Overmap During Autotravel

[ShnitzelX2]

Summary

Interface "toggle to only draw overmap during autotravel"

Purpose of change

Alternative to #75600, see that issue

Describe the solution

Separates the overmap UI from its static function by making a singleton overmap_data held in the game object. By doing this, we can draw the overmap UI e.g. over multiple game turns. This was bound to a toggle key on the overmap, so we can do this while autotraveling:

The time save is significant. For roughly 110 OMTs' uninterrupted drive in a 4x4, the following data was gathered:

Drive Type	Time
TILES	40 sec
TILES with fast travel	24 sec
NO TILES	34 sec
NO TILES with fast travel	22 sec

...and then on foot following the same path,

Walk Type	Time
TILES	20 sec
TILES with fast travel	14 sec
NO TILES	20 sec
NO TILES with fast travel	14 sec

Other Notes:

• This works for both tiled and ASCII overmaps.
• Any UI windows still draw over the overmap, including distractions, "Driving... press 5 or .", etc.
• When travel is finished or interrupted, you are booted out of the overmap.
• It's called "fast travel" in-game for lack of a better name. The toggle is currently bound to 'x', let me know if we want it changed.
• This is meant for traveling a safe or mostly-safe route and is less safe than just autodriving/moving; you only have yourself to blame if you ignore "mi-go spotted!" and end up next to a mi-go.
• This makes it easier to find wandering NPCs and hordes on the overmap.

Describe alternatives you've considered

See original issue

Testing

In addition to the basic tests in the tables above:

• fast travel into a monster
• ..ignoring that monster, then about to crash in vehicle
• ..ignoring that monster on foot
• fast travel while path blocked
• fast travel while grabbing furniture
• fast travel with allies
• fast travel on foot next to projectile shooter (no less safe than without fast travel)

Additional context

Drafted until clang runs and tests run locally