CLI UX: --provider enhancements for more convenient SP descriptions

[rvagg]

--provider should accept:

• http multiaddrs shouldn't require peer ID, they don't get used or validated in any way (yet); figure out how to propagate a non-peer ID through the system, perhaps fake it like we have to with Bitswap in some places.
• http://... and https://... and convert to http multiaddrs, although we'll need to do something about peer ID (see above).
• If the input is recognisably a miner ID (is /f\d+/ enough for that?), look it up on heyfil to see if we can determine addresses for it, e.g. https://heyfil.prod.cid.contact/sp/f0127896
• If the input string can be passed through peer.Decode() then look it up on heyfil to see if it has a miner id, e.g. https://heyfil.prod.cid.contact/sp?peerid=12D3KooWE8yt84RVwW3sFcd6WMjbUdWrZer2YtT4dmtj3dHdahSZ, then do the above to find addresses for it