Pathfinding Visualization, JPS fixes, Misc Improvement (#90233)

## About The Pull Request

[cleans up poor namespacing on light debugging
tools](93cc9070d5)

[Implements a pathfinding visualization
tool](ed91f69ac4)

It holds a set of inputs from the client, and uses them to generate and
display paths from source/target. Left click sets the source, right
click sets the target.

Pathmap support too, if no target is set we display the paths from every
turf in the map to the source, if one is set we build a path TO it from
the source.

I had to add COMSIG_MOB_CLICKON to observers to make this work (tho idk
why it didn't exist already), I also removed the everpresent colorblind
datum from admin datums, only needs to exist if they're using it.

[Adds a mutable_appearance helper that dirlocks them, wallening port
which I thought might be useful here, and will likely be useful
elsewhere in
future](87f752e7c3)

[Fixes an infinite loop in pathmaps if we tried to pull a cached path to
an unreachable target, && not ||
4head](10086a655d)

[Fixes JPS not dealing with border objects properly. They violate some
of the assumptions JPS makes, so we need to backfill them with checks.
These basically read as (if the thing that should normally take this
path can't reach this turf, can
we?)](f56cc4dd43)

## Why It's Good For The Game

Maybe deals with #80619?

Adds more robust testing tools for pathfinding, should allow people to
better understand/debug these systems. I added this with the idea of
adding multiz support but I don't have the time for that rn.

JPS will work around thindows better, that's nice.

https://file.house/IrBiR0bGxoKw1jJJoxgMRQ==.mp4

## Changelog
🆑
fix: Fixed our pathfinding logic getting deeply confused by border
objects
admin: Added clientside displayed pathfinding debug tools, give em a go
/🆑

code/__DEFINES/layers.dm

@@ -307,6 +307,11 @@
 /// Layer for light overlays
 #define LIGHT_DEBUG_LAYER 6
 
+/// Layer for pathfinding arrows
+#define PATH_ARROW_DEBUG_LAYER 7
+/// Layer for pathfinding overlays
+#define PATH_DEBUG_LAYER 8
+
 ///Layer for lobby menu collapse button
 #define LOBBY_BELOW_MENU_LAYER 2
 ///Layer for lobby menu background image and main buttons (Join/Ready, Observe, Character Prefs)