Fixes away map dead slime and AI spawners

- Fixes #2553. Previously,  the away map slime spawner spawned two dead slimes that had living icons. Now it spawns one slime with a dead icon.  These issues are fixed by adding a check for existing slimes at the spawner's location before spawning a slime, and killing the spawned slime via adjustToxLoss() instead of death(). Death() doesn't give the slime a dead icon for some reason.

- Fixes #2533. Previously, the away map AI spawner spawned a dead AI that showed on the PDA messenger at roundstart, showed the BSoD on the AI status displays on the station, and showed up in the round-end report. These issues are fixed by setting the spawned AI's PDA toggle to 1, checking for a key in a dead AI before changing the AI displays, and checking for a mind in AIs before showing their laws at the end of the round so ones that weren't player-controlled aren't shown.

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