[identity] Add verification for replacing a device

Summary:
Added possibility to replace a device in device list

Depends on D11687

Test Plan:

• Added unit tests
• Called UpdateDeviceList RPC with payload that replaced exactly one device - pass
• Called UpdateDeviceList RPC with payload that tried to replace primary device - fail

Reviewers: varun

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D11711