fix: allow multiple minikube profiles to share the same network

[mpobrien]

fixes #14799.

This change makes it possible to start multiple minikube profiles and provide the same value for --network.
Previously, this would fail because both profiles would attempt to use the same IP in that network, and trigger this error:
❌ Exiting due to GUEST_PROVISION: Failed to start host: can't create with that IP, address already in use

The fix here is in pkg/drivers/kic/oci/network_create.go (as suggested by @medyagh in the issue linked above): surface the ContainerIPs that docker network inspect already returns (they were parsed but discarded). Add AllocateFreeContainerIP, which inspects the live container IPs on a network and returns the first unoccupied address starting from gateway+1. This is analogous to how FreeSubnet works for network allocation.
I also made a minor change to pkg/drivers/kic/oci/network.go to handle containers attached to multiple networks. This could be useful if you wanted to attach a shared network to the two profiles after start time.

My use case for this:
I'm working on an application that involves multiple kubernetes clusters, and some of the pods within each cluster will need to send traffic to a pod in another cluster. Modeling that setup with minikube (for testing) isn't possible right now because there's no way for a pod in cluster A to route its traffic to cluster B since they are on separate networks.

I welcome your thoughts!

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• ✅ login: mpobrien / name: Mike O'Brien (1fbac8d)

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[minikube-bot]

Can one of the admins verify this patch?

[nirs]

@mpobrien creating multiple clusters on the same network works for vm drivers (kvm on Linux, vfkit and krunkit on macOS).

Would be nice to make it work also in docker.