feat(net): IP resolution in docker

[emhane]

Enables IP discovery for docker containers that are not connected to the internet, without use of devp2p discovery protocols

[mattsse]

should this just be another natresolver variant?

unsure why this should be a different argument

[emhane]

should this just be another natresolver variant?

unsure why this should be a different argument

sure if you like. what should the variant be called?

[mattsse]

perhaps just netif?

[emhane]

Makes sense to tackle integration into NatResolver as sep issue, since changes the signatures of many functions to be able to return error reading os interfaces @mattsse @onbjerg

[mattsse]

one suggestion

addressed