Temperature Reagent System (#5423)

Overview
This is the github WIP PR for the reagent system project. This is for other developers and users to track progress of the code if they're curious about it, as well as to show that it actually works.

code/unit_tests/chemistry_tests.dm

@@ -0,0 +1,29 @@
+/*
+ *
+ *  Specific Heat Chemistry Test
+ *  Checks if a reagent has a specific heat value.
+ *
+ */
+
+datum/unit_test/specific_heat
+	name = "Chemistry Test - Specific Heat"
+
+datum/unit_test/specific_heat/start_test()
+
+	var/error_count = 0
+
+	for(var/type_found in subtypesof(/datum/reagent/))
+		var/datum/reagent/R = new type_found
+		if(istype(R) && R.id && R.name)
+			if(!SSchemistry.has_valid_specific_heat(R))
+				log_unit_test("[ascii_red][R.type] lacks a proper specific heat value![ascii_reset]")
+				error_count++
+		qdel(R)
+
+	if(error_count)
+		fail("[error_count] reagents(s) found without a proper specific heat value. Assign a specific heat value or make a recipe with these reagents as the final product.")
+	else
+		pass("All reagents have a specific heat value.")
+
+	return 1
+