Runtime should support networking

[xibz]

• runtime should support DNS config
• runtime should support port mapping with host port and container port
• runtime should support port mapping with only container port

[sipsma]

Some preliminary thoughts on this in relation to the CNI support being added to Firecracker-containerd:

The CNI support for Firecracker-containerd allows VMs as a whole to be spun up in a CNI-configured network namespace, so containers that want access to that CNI-configured network need to use their "host" netns (which is actually the Firecracker VM guest's netns).

For CRI-containerd specifically, one valid approach may be to specify that the "sandbox" container use the "host" netns, which will then result in all other containers in the pod using that same netns. This in theory should have an end effect of all containers in the pod have network access to the VM's CNI-configured network.