Add functions for emitting sounds

[xen-000]

Similar to the existing functions in the disabled lua vscript. Right now the only ways to play sounds are quite cumbersome:

• Spawn a point_soundevent via a template and play it, all players will hear this.
• Use play via Instance.ClientCommand, in this case only the given client hears the sound. But its volume is separate from the rest of the game, controllable via snd_toolvolume only.

Ideally the sound API would consist of something like the following:

// Plays a sound event on the entity, returns the sound event GUID to use with SetSoundEventParam
Entity.EmitSound(soundEvent: string): number;

// Plays a sound event on the entity but only the given players can hear it, same return as above
Entity.EmitSoundToPlayers(soundEvent: string, players: CSPlayerController[]): number;

// Sets the given sound event parameter on an active sound event instance, this is what the snd_event_params entity does
// For example "volume" or "pitch"
Instance.SetSoundEventParam(soundEventGUID: number, paramName: string, paramValue: number): void;

// Stops the given sound event instance
Instance.StopSoundEvent(soundEventGUID: number): void;

Perhaps the EmitSound functions could instead return an object representing the sound event instance, and it would then have all the relevant functions.