Add support for Low Power Devices

KNoT requires that KNoT Things and Gateways stay connected for the authentication to stay valid.
This brings extra steps for devices that are operating in low power mode, forcing them to resend authentication data.

The goal for this issue is to enhance the support for Low Power devices and do not require for them to stay up.

No files, tests, or entry points are named in the issue. Start by reviewing the protocol library's authentication and connection handling, then establish how low-power Things and Gateways should remain authenticated without staying connected; done means that behavior is implemented and verified for low-power operation.

Written by the indexing model from the issue text.