load_players should have all IDs from load_roster and load_ff_playerids

[tanho63]

I believe we currently have it that IDs are joined onto load_rosters for backwards compat, but really our primary ID file should be load_players()

thoughts @john-b-edwards @mrcaseb ?

[john-b-edwards]

Did we decide on this or did we want to use nflreadr::load_ff_playerids() instead as the primary ID file?

[tanho63]

We should make load_players the core for nflverse and tack on ff_playerids afterwards imo. This more or less fell through the cracks unfortunately

[mrcaseb]

Players data outsourced to https://github.com/nflverse/nflverse-players