[web] introduce keyserver selection modal
Summary:
This diff introduces the barebones keyserver selection modal. The focus of this diff is just to implement the interface. Subsequent diffs will handle the behavior of disconnect/removing a keyserver from your keyserver selection list
Figma:
Linear task: https://linear.app/comm/issue/ENG-5497/introduce-remove-keyserver-ui
Depends on D9918
Test Plan:
Please see the demo video below
Reviewers: inka, rohan, michal
Reviewed By: inka
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D9920