[MIRROR] Color standardization, vars moved, and signals (#194)

* Color standardization, vars moved, and signals (#52574)

    Defined all the existing light_color values.
    Moved their definitions to colors.dm
    Made white the default color. It was so already, but that was very obscured.
    Moved the atom light-related variables to the atom definition.
    Wrapped changes to variables such as light_color into procs that report the event through signals.
    Moved the light_on variable to the atom level, also adding a signal for its changing, to represent toggling lights.
    Cleaned up a little bit of code in where new variables were defined before redefinitions.

This is all atomization to reduce changes in #52413
None of this affect gameplay at all, it's all code cleaning and refactoring.

There's more colors to standardize, a search for color = will find lots of targets, and I see little need to have both the LIGHT_COLOR and COLOR patterns, but I don't want to make this PR bigger than it already is.

* Color standardization, vars moved, and signals

Co-authored-by: Rohesie <rohesie@gmail.com>

code/modules/assembly/flash.dm

@@ -9,7 +9,7 @@
 	throwforce = 0
 	w_class = WEIGHT_CLASS_TINY
 	custom_materials = list(/datum/material/iron = 300, /datum/material/glass = 300)
-	light_color = LIGHT_COLOR_WHITE
+	light_color = COLOR_WHITE
 	light_power = FLASH_LIGHT_POWER
 	var/flashing_overlay = "flash-f"
 	var/times_used = 0 //Number of times it's been used.