ICMP interconnectivity check

# Background

When I was debugging network issues, I found following checks were often used and might be worthwhile to add as checks:

* Connectivity between two pods on same machine.
* Connectivity between two pods on different machines.
* Connectivity between pod and node on same machine.
* Connectivity between pod and node on different machines.

Each check above should include two ways. That means, one way connectivity doesn't always means ok vice versa.

The issue names no files, tests, or entry points. Start by locating the repository's existing troubleshooting checks and Kubernetes networking helpers, then determine how ICMP checks are structured. Done means covering pod-to-pod and pod-to-node connectivity on the same and different machines, with both directions tested for each pairing.

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