Stats Infrastructure Updates

[aspriddell]

This is going to be a clean-up project based on what we already have and the next generation of stats. As such, some of the old stats will probably need to be removed.

Removals

• [x] Level and alpha pack chances - there's a new api for this
• [x] #351

Fixes

• [x] #344
• [x] #345
• [x] #348

Additions

• [x] #347
• [x] #354
• [ ] add new seasonal api (#341)