[native] Create a roles navigator to handle the role creation flow
Summary:
Since the role creation flow will involve more than one screen, I believe it is necessary (or good to have since it's extendable) to have a role-navigator that will handle its related routes. This diff creates the navigator, and the next few diffs in the stack will use this for navigation. I mainly used the invite links navigator & the community creation navigator as inspiration here.
Depends on D8333
Test Plan: The navigator was tested in the next few diffs as screens for the role creation flow are built out, but locally it works fine and are no issues.
Reviewers: atul, ginsu
Reviewed By: atul
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D8335