Some fixes to autodrive and map memory behavior

[olanti-p]

Summary

SUMMARY: Bugfixes "Fixed a couple issues with autodrive and map memory"

Purpose of change

1. Fix some rare occurences of Called map_memory::get_submap() before initializing map memory region.
2. Make autodrive work at night when not using tiles

Describe the solution

1. Preparing memory map region is now not a hard requirement, but rather an optimization.
   Where before the mm_submaps were searched/loaded/allocated only on preparation step, and get_tile()/get_symbol() would only return data from prepared region, now these heavy operations can potentially happen on every get_* call. This makes it harder to reason about performance, but less prone to breakages.
2. Map memory was never designed as part of game state. It's a graphical overlay, it's state is used by map drawing routines and the occasional "unmemorize vehicle when it moves" hack. Using it for autodrive is hackish, but works. Solution was to encapsulate the hack, and check for either memorized tile or symbol, not just tile (original author probably assumed it was terrain tile id?).

Describe alternatives you've considered

1. It was a bad initial design choice on my part, should've gone with this solution back then.
2. Rewriting map memory from grounds up, to be updated on every turn or avatar action, and memorize actual map data?

Testing

1. I tried reproducing these before, but there's no precise repro steps whenever it gets reported. I'm fairly confident this will solve the issue, but can't verify beyond commenting out prepare_map_memory_region part in cata_tiles.cpp.
2. Autodrive a car in a straight line at day, do a u-turn, set time to night, try autodriving back.
   Without fix: works on tiles mode, fails on text mode. After fix: works on both versions.

[Coolthulhu]

Looks like the comment was for something else.

[olanti-p]

Yeah, copied it but forgot to change afterwards.

[Coolthulhu]

Why does this lose const?

[olanti-p]

Because get_submap() is no longer const. It's either this, or hacky const_cast, or spamming mutable, and this felt least bad.