Adds a unit test that all roundstart spawnable jobs have a landmark to spawn at (#74995)

## About The Pull Request


https://github.com/tgstation/tgstation/pull/74985#issuecomment-1523773626

Tests that all jobs that have `spawn_position > 0` at roundstart have a
location to spawn at.

Also changes the failure message for
`get_default_roundstart_spawn_point` to send to `log_mapping` rather
than `log_world`, as it is a map error and log world doesn't really help
anyone. This would've been sufficient for the existing unit test
`log_mapping`, but that unit test expects that the log has an areacoord
supplied, which we can't really do, given we're reporting a _lack_ of
something.

## Why It's Good For The Game

Stops maps from regressing and dumping people on the latejoin shuttle
roundstart.

## Changelog

~~Not necessary unless I find a map which forgot a landmark~~

🆑 Melbert
fix: Tramstation Robotics and RD now spawn in their departments
roundstart
fix: Birdboat detective now spawns in their office
/🆑

code/datums/map_config.dm

@@ -41,6 +41,9 @@
 	/// List of additional areas that count as a part of the library
 	var/library_areas = list()
 
+	/// List of unit tests that are skipped when running this map
+	var/list/skipped_tests
+
 /**
  * Proc that simply loads the default map config, which should always be functional.
  */
@@ -199,6 +202,16 @@
 				continue
 			library_areas += path
 
+#ifdef UNIT_TESTS
+	// Check for unit tests to skip, no reason to check these if we're not running tests
+	for(var/path_as_text in json["ignored_unit_tests"])
+		var/path_real = text2path(path_as_text)
+		if(!ispath(path_real, /datum/unit_test))
+			stack_trace("Invalid path in mapping config for ignored unit tests: \[[path_as_text]\]")
+			continue
+		LAZYADD(skipped_tests, path_real)
+#endif
+
 	defaulted = FALSE
 	return TRUE
 #undef CHECK_EXISTS