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/modules/unit_tests/mapping.dm

@@ -17,4 +17,3 @@
 			continue
 
 		TEST_FAIL(log_entry)
-