playlists stuff for v2

[pg9182]

For lack of a better place to put it:

• we'll have servers send their playlists to atlas during registration
• playlist names as keys are out -- this has been technically incorrect the whole time as a playlist doesn't necessarily mean a specific game mode
• the playlist names will be transformed to a deterministic hash of the contents
• clients will need to specify the convars they care about it when retrieving the global playlists so we don't have an unbounded response size
  • it will also return the count of convars left out
  • there will be a second hash available of a list of convars asked for by the client (to allow for easier filtering and grouping)

[pg9182]

@ASpoonPlaysGames @RoyalBlue1

[pg9182]

also random note: we probably won't need to do pdata in atlas v2 anymore since we're likely switching to client-side pdata, which will greatly reduce the resource requirements and amount of code in atlas