Allow Citizens to use SMG1 and AR2 alt-fire modes in HL2 and episodic

[pivotman319-owo]

Description

This PR adds support for alt-fire to citizens carrying the following weapons:

• SMG1 (weapon_smg1)
• Combine Pulse Rifle/AR2 (weapon_ar2)

Demonstration video: https://www.youtube.com/watch?v=AsqEgg_6UPU

Citizens carry a limited number of SMG1 grenades and energy balls, governed by the ConVar sk_citizen_grenades and additionally exposed by Hammer integer variable NumGrenades. Several new schedules and tasks (largely adapted from Combine soldier altfire behavior) have also been added, and weapon_smg1 attack handling behavior has also been refactored to support NPC altfire events, with credit given to @Bitl for the initial SMG1 NPC altfire implementation present in Firefight: Reloaded.

The following tasks have been added to CNPC_Citizen:

• TASK_CIT_FACE_TOSS_DIR; aiming towards alt-fire target
• TASK_CIT_GET_PATH_TO_FORCED_GREN_LOS; get acceptable path for forced grenade/energy ball alt-fire
• TASK_CIT_DEFER_SQUAD_GRENADES; delays other squad members' alt-fires by a specified period
• TASK_CIT_PLAY_SEQUENCE_FACE_ALTFIRE_TARGET; invokes SMG1/AR2 alt-fire attack activity

The following schedules have been added to CNPC_Citizen:

• SCHED_CITIZEN_FORCED_GRENADE_FIRE; for FireGrenadeAtTarget input
• SCHED_CITIZEN_AR2_ALTFIRE; Alt-fire schedule
• SCHED_CITIZEN_MOVE_TO_FORCED_GREN_LOS; move to acceptable path for forced grenade/energy ball alt-fire

The following functions have been added to CNPC_Citizen:

• void CNPC_Citizen::SelectScheduleAttack() (called by CNPC_Citizen::SelectScheduleCombat() for the explicit purpose of selecting primary and alt-fire schedules)
• bool CNPC_Citizen::CanAltFireEnemy( bool bUseFreeKnowledge ); check for alt-fire applicability
• int CNPC_Citizen::RangeAttack2Conditions( float flDot, float flDist )
• void CNPC_Citizen::DelayAltFireAttack( float flDelay ); delay alt-fire attack for self
• void CNPC_Citizen::DelaySquadAltFireAttack( float flDelay ); delay alt-fire attack for squad members
• void CNPC_Citizen::InputFireGrenadeAtTarget( inputdata_t& inputdata ); for input FireGrenadeAtTarget

One new input has been added to the in-game entity npc_citizen:

• FireGrenadeAtTarget; Forces an NPC to fire a grenade/energy ball at a target. Accepts an NPC (like an npc_bullseye or npc_combine_s w D_HT relations) as a target parameter.

This depends on #1320 to merge, and additionally requires an FGD update in halflife2.fgd to account for changes in the Citizen code:

@NPCClass base(BaseNPC,Parentname, TalkNPC, PlayerCompanion ) studio() = npc_citizen : "Citizen"
[

	// [...]

	NumGrenades(choices) : "Number of Grenades" : "3" : "How many SMG1 grenades/AR2 energy balls does this citizen have? Select 'None' to disable alt-fire modes." =
	[
		"0" : "None"
		"1" : "1"
		"2" : "2"
		"3" : "3"
		"4" : "4"
		"5" : "5"
		"999999" : "Unlimited"
	]
	
	// [...]
	
	//Inputs
	// [...]
	input FireGrenadeAtTarget(string) : "Fire a grenade or AR2 energy ball at the target. The citizen MUST have an SMG1 or AR2 equipped!"

	// [...]
]