lowpop gamemodes, plus a little extra

[Darkmajia]

adds specific gamemodes for lowpop after regular complaints about it, resolving #569 and #768

this is accomplished with a lowpop limiter gamerule that prevents presets with it from rolling above 19 players, and a midpop limiter gamerule that prevents presets with it from rolling below 20 players. a maxPlayers functionality had to be added to a bunch of checks to ensure that lowpop gamemodes do NOT roll past the 19 player mark. these values can be adjusted easily and inserted into new presets without issue

all lowpop gamerules have a different antag event table that removes midround crew antags like sleeper agents and changeling awakening, as well as lone operatives. other ghost role antags like rat kings and dragons (though dragon is 30 pop minimum) are still included

also fixed a minor issue with the svs (sleeperless) antag event table that prevented listening post and any future delta v antag gamerules from spawning during it

the current lowpop gamemode distribution is:

• traitor, 50% (inherits the 5 minimum population requirement from the base traitor rule)
• thief, 25%
• survival, 20% (2 round cooldown)
• extended, 5% (1 round cooldown)

notably, kessler is gone entirely from lowpop

Changelog
🆑

• add: Rounds below 20 players now have their own gamemodes with a reduced threat level.
• fix: Listening Post can now spawn during Spy vs Spy rounds.

[kipdotnet]

Youre my hero forever btw. Have I said that