[lib] introduce new device list function to replace keyserver device

Summary:
we want to be able to replace an existing keyserver with a new one

Depends on D12734

Test Plan: later in the diff stack I successfully replace my existing keyserver device with a new one

Reviewers: bartek, ashoat

Reviewed By: bartek

Subscribers: tomek

Differential Revision: https://phab.comm.dev/D12805