Network probes are configured with the specs, and provide their output
as a status.
At the moment only platform code can configure network probes.
If any network probes are configured, they affect network.Status
'Connectivity' flag.
Example, create the probe:
```
talosctl -n 172.20.0.3 meta write 0xa '{"probes": [{"interval": "1s", "tcp": {"endpoint": "google.com:80", "timeout": "10s"}}]}'
```
Watch probe status:
```
$ talosctl -n 172.20.0.3 get probe
NODE NAMESPACE TYPE ID VERSION SUCCESS
172.20.0.3 network ProbeStatus tcp:google.com:80 5 true
```
With failing probes:
```
$ talosctl -n 172.20.0.3 get probe
NODE NAMESPACE TYPE ID VERSION SUCCESS
172.20.0.3 network ProbeStatus tcp:google.com:80 4 true
172.20.0.3 network ProbeStatus tcp:google.com:81 1 false
$ talosctl -n 172.20.0.3 get networkstatus
NODE NAMESPACE TYPE ID VERSION ADDRESS CONNECTIVITY HOSTNAME ETC
172.20.0.3 network NetworkStatus status 5 true true true true
```
Signed-off-by: Andrey Smirnov <andrey.smirnov@talos-systems.com>
