Initial port of ItemPolicy

[Nomagno]

• ItemPolicy is a system for determining the rules of a race, as pertaining to which collectibles can spawn, and several types of automatic item "dispensation" upon pass by the start/finish line
• It also includes a system to forbid lappings and lappers from hitting each other, and a virtual pace car/virtual safety car system
• It allows to set different rules for different sections of a race, each section defined by the lap its start
• The current implementation is adapted from STK TME to STK 1.0+command manager, hence only doing the server side business
• Known current issues as of initial implementation commit:
• • IMPORTANT: in the current implementation, each collectible "voluntarily despawns itself" after checking the current itempolicy section in its ::update(). This needs to be force synced to the client somehow in 1.0. for item boxes and nitro, this doesn't cause basically any lag even if it's strange, but for bananas it does cause lag so it should be fixed BEFORE MERGING.
• • a pit stop slowdown is applied in TME when a virtual pace car restart is underway. This penalty type doesn't exist in 1.0, so it's replaced with a bubblegum slowdown. However, it's not really synced properly even though it should be synced properly. The slowdown is slow enough it doesn't cause any serious lag, so fine for now.

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[kimden]

Mostly stylistic comments and things I noticed without opening IDE

[kimden]

Please adhere to code style.