connect mode: ap_only, sta_only, sta_ap mode

WIP: A Hybrid Node is a node which is only connected to the mesh as a station. AP interface is free for user. There are some use cases where this can be useful:

• Battery supplied nodes. A node that is running from battery must use deep sleep to extend runtime. It will only be active during a short time every some minutes or hours. They should not expose AP interface to mesh to avoid connection failures.
• Nodes connected to mesh and external network. It may be desired for some specific node that AP is free to be used on user code for a different task. It could be used to run an embedded web server to allow data extraction from mesh.
• Nodes in the physical mesh limit. In that case it may be desired not to extend AP coverage to hide it as much as possible.