Remove Firefox Account related code
While updating Ceno to Android-Components v121, I noticed that we still have some Fxa (Firefox Account) related code included in Ceno. I don't think it does much because we have no way for users to log into a firefox account and we don't exposed the account related features. Still, we should remove any unused code that references Fxa, so we make sure that Ceno doesn't ping Mozilla's servers unnecessarily.
I would start by simply removing this entire BackgroundServices.kt file and see what that breaks and if we can remove/replace those parts also.
This may also just be the start of a larger clean up of the code base to remove any unused or commented out code that is enlarging the size of our apks.