Gather configuration capabilities in Stork Agent

It is related to: https://gitlab.isc.org/isc-projects/stork/-/wikis/designs/config-design#configuration-capabilities

Stork Agent must check configuration capabilities of detected apps. The server will use the capabilities from the agent to decide what configuration changes and how it can apply to the monitored apps. The UI client will also use the capabilities to show and hide the configuration views. This ticket is focused on gathering the capabilities in the agent and making them available to the server.