Roundstart xenomorph count changes (#6291)

# About the pull request
Changes roundstart xeno amounts to try to keep a 1:3 to 1:4 xeno to
combat role ratio
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# Explain why it's good for the game
https://imgur.com/5dSXlmX
This is just an example but this image is taken pre-drop and there are
23 (25 if you count IOs who do not take part on the front for the most
part) compared to 12 xenos (one died to pred), the goal was always to
keep a 1:3 or 1:4 ratio and it is currently not working and causing
lowpop rounds to be onesided steamrolls.
Every time marines win in lowpop you hear after the round from xenos "we
had 7 burrowed" so yeah something here is wrong.
# Testing Photographs and Procedure
<details>
<summary>Screenshots & Videos</summary>

Put screenshots and videos here with an empty line between the
screenshots and the `<details>` tags.

</details>


# Changelog
:cl:
balance: Latejoin marines to larva ratio changed to 1:4 for the first 15
minutes, going back to 1:2.5 afterwards.
/:cl:

code/__DEFINES/mode.dm

@@ -77,6 +77,7 @@
 #define ROUNDSTATUS_FOG_DOWN 1
 #define ROUNDSTATUS_PODDOORS_OPEN 2
 
+#define LATEJOIN_MARINES_PER_LATEJOIN_LARVA_EARLY 4
 #define LATEJOIN_MARINES_PER_LATEJOIN_LARVA 2.5
 
 //=================================================

code/game/gamemodes/cm_initialize.dm

@@ -74,6 +74,7 @@ Additional game mode variables.
 	var/monkey_amount = 0 //How many monkeys do we spawn on this map ?
 	var/list/monkey_types = list() //What type of monkeys do we spawn
 	var/latejoin_tally = 0 //How many people latejoined Marines
+	var/latejoin_larva_drop_early = LATEJOIN_MARINES_PER_LATEJOIN_LARVA_EARLY
 	var/latejoin_larva_drop = LATEJOIN_MARINES_PER_LATEJOIN_LARVA //A larva will spawn in once the tally reaches this level. If set to 0, no latejoin larva drop
 	/// Amount of latejoin_tally already awarded as larvas
 	var/latejoin_larva_used = 0

code/modules/mob/new_player/new_player.dm

@@ -267,8 +267,13 @@
 			sq.max_engineers = engi_slot_formula(GLOB.clients.len)
 			sq.max_medics = medic_slot_formula(GLOB.clients.len)
 
-	if(SSticker.mode.latejoin_larva_drop && SSticker.mode.latejoin_tally - SSticker.mode.latejoin_larva_used >= SSticker.mode.latejoin_larva_drop)
-		SSticker.mode.latejoin_larva_used += SSticker.mode.latejoin_larva_drop
+	var/latejoin_larva_drop = SSticker.mode.latejoin_larva_drop
+
+	if (ROUND_TIME < XENO_ROUNDSTART_PROGRESS_TIME_2)
+		latejoin_larva_drop = SSticker.mode.latejoin_larva_drop_early
+
+	if(latejoin_larva_drop && SSticker.mode.latejoin_tally - SSticker.mode.latejoin_larva_used >= latejoin_larva_drop)
+		SSticker.mode.latejoin_larva_used += latejoin_larva_drop
 		var/datum/hive_status/hive
 		for(var/hivenumber in GLOB.hive_datum)
 			hive = GLOB.hive_datum[hivenumber]