core: Add releasing resources after disconnection
core: Add releasing resources after disconnection

This patch tracks disconnection events, releasing resources after
Radio/Unix transport, and Cloud initiated disconnections.

CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source,CESARBR/knot-service-source