Refactors pickups into Prefabs, then adds MoneyPickup prefab (adds score)

[benvinegar]

This PR has a couple changes:

• Refactors Pickups into individual prefabs
• Adds a effectDuration property to Pickup prefabs
• Refactors how effects expire inside Player
• Tries to DRY up some code
• Adds a new MoneyPickup prefab that scores you 500 pts (nothing else)
• Tweaks score values for other pickups

[benvinegar]

one tiny nit: the money pickup doesn't have a text popup like the other pickups, so it might not be super clear what it does

Yeah I noticed that too. Maybe worth a followup.