[lib] introduce selected keyservers selector

Summary:
In order to populate the list of selected keyservers the user has added, we need to introduce this selector which selects all the keyserver infos in the keyserver store and additionally appends the keyserver admin username

Linear task: https://linear.app/comm/issue/ENG-5370/introduce-connected-keyservers-selector

Depends on D9639

Test Plan:
Logged out the result of the selector and got the following (the second keyserver is just a test "dummy" keyserver I added to the keyserver store when testing the add keyserver flow)

Reviewers: inka, michal, rohan

Reviewed By: rohan

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9641