Add more Onionoo metadata fields: `version` should be the protocol version and `build_revision` the NetworkStatus API revision used

I think it is useful to understand the network status better if we add/change metadata fields currently produced by Onionoo:

• version: should be the protocol version behind the results delivered. We could be flexible here and start with a new versioning for the API or we can just use 8.3 if we speak the whole Onionoo one. (Note: this implies to change what the API currently replies for version as that seems to be a Tor version, which is a bit weird as there is usually more than one Tor version available (and recommended) simultaneously)
• build_revision: should be the NetworkStatus API commit (hash) that is responsible for the reply. That has been useful in the past when debugging Onionoo issues, in particular related to the data shown on relay search, and I expect it will be useful for the NetworkStatus API.