Antag HUDs will now animate if you have multiple antagonists, and will no longer clear on deconversion (#62718)

About The Pull Request

This is for the admin combo HUD. Players shouldn't notice any difference (except at roundend).
2021-11-09T16-27-26.mp4

Removes the ability to set custom antag HUDs for custom admin teams for complexity, though if there's a large enough demand I can try to bring it back in another PR.

Fixes #59767

TM candidate only so that I can make sure antags aren't getting leaked to people who shouldn't see them.
Changelog

cl
fix: Antag HUDs will no longer clear on deconversion if the player was another antag.
qol: Antag HUDs (as seen by admins and at the round end) will now animate between all antagonists, rather than just choosing the most latest.
/cl

code/controllers/subsystem/processing/antag_hud.dm

@@ -0,0 +1,4 @@
+PROCESSING_SUBSYSTEM_DEF(antag_hud)
+	name = "Antag HUDs"
+	flags = SS_NO_INIT
+	wait = 2 SECONDS