Refactors operating tables to be event driven + QoL + Unit Test (#69015)

* Event driven table

* Operating computer fix + loosening of check

* Unit testing

* IT NEEDS TO BE FORCE MOVE YOU GOTTA CLIMB TABLES AAAAH

* Migrated patient to carbon instead of human
Has no real bearing on the experiments tbh

* DNAs can be null apparently

* Simplify replacement code

* Move comments

code/modules/unit_tests/_unit_tests.dm

@@ -120,6 +120,7 @@
 #include "ntnetwork_tests.dm"
 #include "nuke_cinematic.dm"
 #include "objectives.dm"
+#include "operating_table.dm"
 #include "outfit_sanity.dm"
 #include "paintings.dm"
 #include "pills.dm"

code/modules/unit_tests/operating_table.dm

@@ -0,0 +1,32 @@
+/// Make a mob hop on an optable, rest, get up, rest again, and then move to another tile.
+/// While the mob is still an active patient, move another mob in too.
+/// This is so the replacement code can kick in when the original mob is no longer valid.
+/datum/unit_test/operating_table
+
+/datum/unit_test/operating_table/Run()
+	var/obj/structure/table/optable/table = allocate(/obj/structure/table/optable)
+	var/mob/living/carbon/human/human = allocate(/mob/living/carbon/human, get_step(table, NORTH))
+	var/mob/living/carbon/human/replacement_human = allocate(/mob/living/carbon/human, get_step(table, NORTH))
+	
+	// Resting is a bit more high level than bodypos, gets us nicer coverage.
+	human.set_resting(new_resting = FALSE, instant = TRUE)
+	replacement_human.set_resting(new_resting = FALSE, instant = TRUE)
+
+	human.forceMove(get_turf(table))
+	TEST_ASSERT_NULL(table.patient, "Operating table is occupied by a non-resting patient.")
+
+	human.set_resting(new_resting = TRUE, instant = TRUE)
+	TEST_ASSERT_EQUAL(table.patient, human, "Operating table failed to update for a resting patient.")
+
+	human.set_resting(new_resting = FALSE, instant = TRUE)
+	TEST_ASSERT_NULL(table.patient, "Operating table is occupied by a non-resting patient.")
+
+	human.set_resting(new_resting = TRUE, instant = TRUE)
+	TEST_ASSERT_EQUAL(table.patient, human, "Operating table failed to update for a resting patient.")
+
+	replacement_human.forceMove(get_turf(table))
+	replacement_human.set_resting(new_resting = TRUE, instant = TRUE)
+	TEST_ASSERT_EQUAL(table.patient, human, "Operating table patient unset by another patient jumping in.")
+
+	human.forceMove(get_step(get_turf(table), NORTH))
+	TEST_ASSERT_EQUAL(table.patient, replacement_human, "Operating table failed to find a replacement patient.")