Auth instances cleanup

[SUPERCILEX]

@samtstern While working on the anonymous auth PR, it was frustrating to have to pass in flow params each time I wanted to get an auth or user instance. This PR fixes that issue with a slightly hacky solution of storing the flow params in a static variable that's reset each time the helper activity is created.

This PR is built on top of #785 which is built on top of #784.

[samtstern]

This change strikes me as a little strange. We've avoided, until now, keeping FlowParams as static. Instead each Activity and Fragment has kept the flow params as a member variable and passed it along through the flow.

If we do this change, then we'd have a mixed approach. A more consistent thing to do would be to make this change and then add a static FlowParameters getFlowParams() method to AuthInstances but I don't really like that idea since static variables are generally code smell.

[SUPERCILEX]

@samtstern Yeah, upon looking back at this PR it does seem kinda gross. I've updated it to convert the AuthInstances into an AuthHelper object. While I know you were trying to get rid of the helpers, I feel like keeping a simple and contained helper just for the auth stuff makes sense and reduces the bloat of having to pass in those FlowParams each time. What do you think?

[SUPERCILEX]

@samtstern Well that was rough. Finally got the build to pass though! 😄

[samtstern]

Sorry I forgot about this, I am fine with this change!

[SUPERCILEX]

@samtstern awesome possum! 😀