prop224: Add a consensus param to enable/disable next gen onion service
We need a consensus parameter that controls the deployment of proposal 224 that is next generation onion service.
Lots of code will go in tor without being used at first so this parameter will tell all the tor out there to start using the new generation onion service.
This is especially important before we merge HSDir support (#17238 (moved)) in order for relay to NOT store 224 descriptors while the rest is under development.
OnionService224=0 (or we can omit 224 here and assume "OnionService" is next gen obviously :).