[identity] Implement RPC for secondary device registration

Summary:
Implementation of RPC from D10861.

• Created function to put device data into device list (device key upload)
• Called this function along with access token creation from the RPC handler
• Performed basic device list checks - the RPC fails if the device is not on the device list.

Depends on D10861, D11072, D11073

Test Plan:
Tested both scenarios: device on device list and device not on device list.

• If the device is not on the list, fails with permission denied status
• When the device is on the list, the RPC succeeds and returns the access token. Used awslocal dynamodb scan to make sure device keys are put in the devices table under userID|device-{deviceID} primary key.

Reviewers: varun, michal

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10862