Adding SSpathfinding.

[MistakeNot4892]

Description of changes

• Adding a subsystem to handle scheduling/tick checking of A* pathfinding.
• Converts bots and ICs to use the subsystem.
• Adds handling for paths to mob automove.
• Should fix or at least limit/mitigate #4058.

TODO

• [X] Coarse implementation.
• [ ] Get bots to actually work again.
• [x] Get path following, updating and invalidation working on a test mob controller type.
• [x] Test asynchronous/tick checked AStar().

Why and what will this PR improve

• Allows use of A* without locking up the entire game.
• Generalizes pathfinding off the bot subtype so mob controllers in general can use it.

Authorship

Myself.

Changelog

Nothing player-facing.