Oxygen is Toxic to the Vox, Plasma Heals Plasmamen, Plasmaman Suit Autoextinguishes, Oxygen Burns Plasmamen

Oxygen is toxic to the Vox (as toxic as plasma).
Plasma healing plasmaman from swindly @
https://github.com/tgstation/tgstation/pull/24209
Plasmaman suit auto-extinguishing actually does something now.
Oxygen burns Plasmamen.

code/__DEFINES/flags.dm

@@ -23,6 +23,7 @@
 
 #define BLOCK_GAS_SMOKE_EFFECT	8192	// blocks the effect that chemical clouds would have on a mob --glasses, mask and helmets ONLY!
 #define THICKMATERIAL 			8192	//prevents syringes, parapens and hypos if the external suit or helmet (if targeting head) has this flag. Example: space suits, biosuit, bombsuits, thick suits that cover your body. (NOTE: flag shared with BLOCK_GAS_SMOKE_EFFECT)
+#define AUTOEXTINGUISH			16384	// Suits that have this will automatically extinguish a burning mob when worn.
 
 //Reagent flags
 #define REAGENT_NOREACT			1
@@ -43,6 +44,7 @@
 #define ALL_RPARTS		2048
 #define NOGUNS			4096
 #define NOTRANSSTING	8192
+#define PLASMA_BASED	16384
 
 //Species clothing flags
 #define HAS_UNDERWEAR 	1