[keyserver] uploadSecondaryDeviceKeysAndLogIn client method
Summary:
we will call this after the keyserver has been added to th device list by the primary device
Depends on D12151
Test Plan: tested in next diff by calling the RPC with a signed nonce
Reviewers: bartek
Reviewed By: bartek
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D12155