Offer a way to validate the host

[PietroPasotti]

when automating the deployment of parca and parca-agent, we have an issue:
we can't assume that the user is running the process on a kernel with the right BPF flags and support enabled.
The only thing we can do is try to start parca, see it fail, (grep the logs?)

A thought about how we could solve this is offer a separate tool (something like validate-host?) or add a CLI flag to parca that exits zero iff the system can load bpf programs