[native] Add a custom TabNavigator

Summary: I add a custom router and navigator for TabNavigator. In later diffs, the new router will be used to prevent the user from tab navigating in edit mode.

Test Plan:
On iOS:

• Open the app.
• Navigate between tabs.

Reviewers: michal, inka, ashoat, tomek

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D8303