[native] Add selection state to KeyserverSelection

Summary:
This diff adds React state for selection and the corresponding styles to match what's in Figma. To handle this in RegistrationTile I also introduce a React context that is internal to that file.

Depends on D7576

Test Plan:

before	after

Reviewers: ginsu, atul

Reviewed By: atul

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D7577