[native] introduce ConnectFarcaster registration screen

Summary:
This diff introduces the barebones ConnectFarcaster registration screen + all the navigational logic needed for it. Decided to break the full introduction into multiple diffs so that this it is easier to review so subsquent diffs will handle extending this component to match what we had during the hackathon

Depends on D11441

Test Plan:
Please see screenshot to see what the screen looks like + tested the entire sign in flow during the hackathon

Reviewers: atul

Reviewed By: atul

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11442