[native] introduce barebones keyserver selection bottom sheet to root navigator

Summary:
This diff introduces the barebones keyserver selection bottom sheet component as well as all the necessary logic needed to add this to the root navigator to eventually route to it. Subsquent diffs will handle fully introducing the UI and all the other functionality needed for this bottom sheet

Linear task: https://linear.app/comm/issue/ENG-5472/add-keyserverselectionbottomsheet-to-the-root-navigator

Depends on D9725

Test Plan: Confirmed that I was able to get to this barebones bottomsheet when I pressed on a keyserver selection list item

Reviewers: rohan, inka, michal

Reviewed By: inka

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9726