[MERGED PR] Makes security slots scale at lower population

[LeahTheTech]

I've addressed the cryoing issue Jelly brought up by doing this: https://github.com/goonstation/goonstation/pull/18145
I'm not a fan of separating the two servers mechanically, and I really don't think this will have too much of an impact on classic as things stand. Also overstaffed security teams are an issue on classic sometimes too.