Move firebase functionality out of /lib/game-saving/account.ts into its own file

[Cosmin-Mare]

At the moment, all the firebase API functionality is inside /lib/game-saving/accounts.ts and it should be its own lib file(dbUtils.ts), because other future functionality involving the db may not directly involve game-saving, or accounts.

[JosiasAurel]

i would advocate for using a filename firebase.ts instead