Adds an universal object health system. (#21266)

https://www.youtube.com/watch?v=ZpUYjpKg9KY

As per title. The goal is to add health to most objects in the game and
thus allow them to be dynamically destructible, while also avoiding
shitcode like each structure having its own snowflake health update
proc.

---------

Signed-off-by: Matt Atlas <mattiathebest2000@hotmail.it>
Co-authored-by: Matt Atlas <liermattia@gmail.com>
Co-authored-by: SleepyGemmy <99297919+SleepyGemmy@users.noreply.github.com>

code/modules/modular_computers/computers/modular_computer/variables.dm

@@ -3,6 +3,8 @@
 /obj/item/modular_computer
 	name = "Modular Computer"
 	desc = DESC_PARENT
+	maxhealth = OBJECT_HEALTH_MEDIUM
+	should_use_health = TRUE
 
 	var/lexical_name = "computer"
 	/// Whether the computer is turned on.
@@ -94,13 +96,8 @@
 	var/power_has_failed = FALSE
 	var/is_holographic = FALSE
 
-	/// Damage of the chassis. If the chassis takes too much damage it will break apart.
-	/// Current damage level
-	var/damage = 0
 	/// Damage level at which the computer ceases to operate
 	var/broken_damage = 50
-	/// Damage level at which the computer breaks apart.
-	var/max_damage = 100
 
 	/// Important hardware (must be installed for computer to work)
 	/// CPU. Without it the computer won't run. Better CPUs can run more programs at once.