Implemented the RPC for primary device logout. It:

• Verifies if the RPC is called by a primary device
• Validates received device list: if it is a singleton of the primary device
• Applies the updated device list
• Revokes user device's CSATs
• Removes devices' data and OTKs

Depends on D12571, D12589

Created a user with a few devices. Used function from D12586 to call this RPC:

• It failed when called from secondary device
• It failed when deliberately malformed the device list payload or used a different device ID
• It succeeded when called from primary device. Verified DDB:
  • Users table item was still there
  • Devices table contained the singleton device list. No device data was present
  • OTKs and tokens were gone