Rework map pools & add map vote picker

[Pablete1234]

Reworks a few aspects in map pools, and makes the voted pool use a MapVotePicker to decide what maps go on the vote, as well as handling the score to weight conversion via a custom formula defined in the config.
This extra step allows for arbitrary modifications to score for extra functionality such as:

• lowering weights for gamemodes that already got representation on the vote (eg: if first map is CTW, CTW is less likely to appear in the following picks)
• Current online playercount to map size ratio (prefer playing maps of proper size over wrongly-sized ones).
• Allow tweaking via config values all of the internal dials that affect this, so they can be fine-tuned in production

[Electroid]

Approved, but minor changed requested.

[Electroid]

Thanks for landing these improvements! Excited 🎉