We should improve the checkups for networking

[directionless]

We have some checkups relating to network stuff.

There's network info which is great. But connectivity could be improved. Today is is a fairly simple check, but as compared with the old log checkpoint it's missing:

• dns resolution
• server version fetching

And then, as underscored today, we should also add:

• a flare to measure upload and download speed (this may need server support)

I don't know if this should be 1 flare, or several.