Adds two heavy midround rulesets, mass traitors and mass changelings (#93447)

## About The Pull Request

- [ ] I tested this pr

Adds "Midround Mass Traitors" and "Midround Mass Changelings" heavy
rulesets

Midround Mass Traitors will turn a number of the crew into sleeper
agents

Midround Mass Lings will spawn a number of changeling meteors 

BY DEFAULT:
- Traitors will spawn 2-4 sleeper agents
- Lings will spawn 2-3 changeling meteors
- They won't run without >=2 candidates
- They have no config blacklist (so the HoP can roll mass midround
traitor, despite not being able to roll normal midround traitor. However
default blacklisted roles like security officers are still blocked)
- They're weighted impossible on tier 0, same weight as most midrounds
on tier 1, and fairly high on tiers 2 and 3
- They're repeatable but very unlikely to repeat
- Significantly higher min pop brackets than their solo counter part

## Why It's Good For The Game

Adds more options for lategame antags than big midrounds

## Changelog

🆑 Melbert
add: Two new heavy dynamic rulesets: "Midround Mass Traitors" and
"Midround Mass Changelings"
/🆑

code/controllers/subsystem/dynamic/__dynamic_defines.dm

@@ -43,6 +43,9 @@
 /// Ruleset can be configured by admins (implements /proc/configure_ruleset)
 /// Only implemented for midrounds currently
 #define RULESET_ADMIN_CONFIGURABLE (1<<2)
+/// Applied to rulesets which intentionally share a pref_flag with another rulesets
+/// Denotes multiple rulesets which abide by the same preference, but are each a variation of some base ruleset
+#define RULESET_VARIATION (1<<3)
 
 /// Href for cancelling midround rulesets before execution
 #define MIDROUND_CANCEL_HREF(...) "(<a href='byond://?src=[REF(src)];admin_cancel_midround=[REF(picked_ruleset)]'>CANCEL</a>)"

code/controllers/subsystem/dynamic/_dynamic_ruleset.dm

@@ -10,9 +10,12 @@
 	/// Don't change this unless you know what you're doing.
 	var/config_tag
 
-	/// What flag to check for jobbans? Optional, if unset, uses pref_flag
+	/// What flag to check for jobbans?
+	/// Optional, if unset, uses pref_flag for jobbans instead
 	var/jobban_flag
-	/// What flag to check for prefs? Required if the antag has an associated preference
+	/// What flag to check for prefs?
+	/// Required if the antag has an associated preference, and must be unique
+	/// (unless RULESET_VARIATION is set in ruleset_flags)
 	var/pref_flag
 	/// Flags for this ruleset
 	var/ruleset_flags = NONE

code/controllers/subsystem/dynamic/dynamic_ruleset_midround.dm

@@ -658,7 +658,7 @@
 	candidate_role = "Changeling"
 	pref_flag = ROLE_CHANGELING_MIDROUND
 	jobban_flag = ROLE_CHANGELING
-	ruleset_flags = RULESET_INVADER
+	ruleset_flags = RULESET_INVADER|RULESET_VARIATION
 	weight = 5
 	min_pop = 15
 	max_antag_cap = 1
@@ -670,6 +670,21 @@
 /datum/dynamic_ruleset/midround/from_ghosts/space_changeling/assign_role(datum/mind/candidate)
 	generate_changeling_meteor(candidate)
 
+/datum/dynamic_ruleset/midround/from_ghosts/space_changeling/mass
+	name = "Mass Space Changelings"
+	config_tag = "Mass Changelings"
+	midround_type = HEAVY_MIDROUND
+	min_pop = 25
+	min_antag_cap = 2
+	max_antag_cap = 3
+	repeatable_weight_decrease = 4
+	weight = list(
+		DYNAMIC_TIER_LOW = 0,
+		DYNAMIC_TIER_LOWMEDIUM = 3,
+		DYNAMIC_TIER_MEDIUMHIGH = 4,
+		DYNAMIC_TIER_HIGH = 5,
+	)
+
 /datum/dynamic_ruleset/midround/from_ghosts/paradox_clone
 	name = "Paradox Clone"
 	config_tag = "Paradox Clone"
@@ -1064,6 +1079,7 @@
 	false_alarm_able = TRUE
 	pref_flag = ROLE_SLEEPER_AGENT
 	jobban_flag = ROLE_TRAITOR
+	ruleset_flags = RULESET_VARIATION
 	weight = 10
 	min_pop = 3
 	blacklisted_roles = list(
@@ -1079,6 +1095,22 @@
 		"[command_name()] High-Priority Update",
 	)
 
+/datum/dynamic_ruleset/midround/from_living/traitor/mass
+	name = "Mass Traitors"
+	config_tag = "Mass Traitors"
+	midround_type = HEAVY_MIDROUND
+	min_pop = 15
+	min_antag_cap = 2
+	max_antag_cap = 4
+	repeatable_weight_decrease = 8
+	blacklisted_roles = list()
+	weight = list(
+		DYNAMIC_TIER_LOW = 0,
+		DYNAMIC_TIER_LOWMEDIUM = 3,
+		DYNAMIC_TIER_MEDIUMHIGH = 8,
+		DYNAMIC_TIER_HIGH = 10,
+	)
+
 /datum/dynamic_ruleset/midround/from_living/malf_ai
 	name = "Malfunctioning AI"
 	config_tag = "Midround Malfunctioning AI"