Embryo 1s Spawn Protection (#7728)

# About the pull request

This PR adds a 1s spawn protection window when larva bursts from an
embryo. The mob has godmode for this duration and will signal no ignite.
The `RECENTSPAWN` flag helps identify a temporary godmode, and is what
also makes all bullets miss temporarily.

This also can be a useful admin tool since the time is variable callable
on any living mob.

# Explain why it's good for the game

Unnested bursts are already near suicide for someone to take. This
should hopefully make a narrow escape possible. Marines can still trap
bursts, but merely shooting the burst immediately will no longer work
for 1s.

# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

https://youtu.be/u1PXcbKuUWc

</details>


# Changelog
:cl: Drathek
add: Chestbursters now have spawn protections for 1s (godmode, evasion,
and ignores fire)
/:cl:

code/__DEFINES/mobs.dm

@@ -113,7 +113,7 @@
 #define CANROOT (1<<6)
 #define GODMODE (1<<12)
 #define FAKEDEATH (1<<13) //Replaces stuff like changeling.changeling_fakedeath
-//#define DISFIGURED (1<<14) //unused
+#define RECENTSPAWN (1<<14) // Temporarily invincible via GODMODE
 #define XENO_HOST (1<<15) //Tracks whether we're gonna be a baby alien's mummy.
 #define IMMOBILE_ACTION (1<<16) // If you are performing an action that prevents you from being pushed by your own people.
 #define PERMANENTLY_DEAD (1<<17)

code/_globalvars/bitfields.dm

@@ -360,6 +360,7 @@ DEFINE_BITFIELD(status_flags, list(
 	"PASSEMOTES" = PASSEMOTES,
 	"GODMODE" = GODMODE,
 	"FAKEDEATH" = FAKEDEATH,
+	"RECENTSPAWN" = RECENTSPAWN,
 	"XENO_HOST" = XENO_HOST,
 	"IMMOBILE_ACTION" = IMMOBILE_ACTION,
 	"PERMANENTLY_DEAD" = PERMANENTLY_DEAD,

code/modules/mob/living/carbon/xenomorph/Embryo.dm

@@ -326,6 +326,7 @@
 	for(var/mob/living/carbon/xenomorph/larva/larva_embryo in victim)
 		var/datum/hive_status/hive = GLOB.hive_datum[larva_embryo.hivenumber]
 		larva_embryo.forceMove(get_turf(victim)) //moved to the turf directly so we don't get stuck inside a cryopod or another mob container.
+		larva_embryo.grant_spawn_protection(1 SECONDS)
 		playsound(larva_embryo, pick('sound/voice/alien_chestburst.ogg','sound/voice/alien_chestburst2.ogg'), 25)
 
 		if(larva_embryo.client)

code/modules/mob/living/living_health_procs.dm

@@ -476,6 +476,20 @@
 		client.soundOutput.status_flags ^= EAR_DEAF_MUTE
 		client.soundOutput.apply_status()
 
+/mob/living/proc/grant_spawn_protection(duration)
+	status_flags |= RECENTSPAWN|GODMODE
+	RegisterSignal(src, list(COMSIG_LIVING_FLAMER_CROSSED, COMSIG_LIVING_FLAMER_FLAMED), PROC_REF(handle_fire_protection))
+	addtimer(CALLBACK(src, PROC_REF(end_spawn_protection)), duration)
+
+/mob/living/proc/end_spawn_protection()
+	status_flags &= ~(RECENTSPAWN|GODMODE)
+	UnregisterSignal(src, list(COMSIG_LIVING_FLAMER_CROSSED, COMSIG_LIVING_FLAMER_FLAMED))
+
+/mob/living/proc/handle_fire_protection(mob/living/living, datum/reagent/chem)
+	SIGNAL_HANDLER
+	if(status_flags & (RECENTSPAWN|GODMODE))
+		return COMPONENT_NO_IGNITE
+
 // heal ONE limb, organ gets randomly selected from damaged ones.
 /mob/living/proc/heal_limb_damage(brute, burn)
 	apply_damage(-brute, BRUTE)

code/modules/projectiles/projectile.dm

@@ -545,7 +545,7 @@
 		to_world(SPAN_DEBUG("([L]) Hit chance: [hit_chance] | Roll: [hit_roll]"))
 		#endif
 
-		if(hit_chance > hit_roll)
+		if(hit_chance > hit_roll && !(L.status_flags & RECENTSPAWN))
 			#if DEBUG_HIT_CHANCE
 			to_world(SPAN_DEBUG("([L]) Hit."))
 			#endif