hs-v3: Require reasonably live consensus

Some days before this commit, the network experienced a DDoS on the directory authorities that prevented them to generate a consensus for more than 5 hours straight.

That in turn entirely disabled onion service v3, client and service side, due to the subsystem requiring a live consensus to function properly.

We know require a reasonably live consensus which means that the HSv3 subsystem will to its job for using the best consensus tor can find. If the entire network is using an old consensus, than this should be alright.

If the service happens to use a live consensus while a client is not, it should still work because the client will use the current SRV it sees which might be the previous SRV for the service for which it still publish descriptors for.

If the service is using an old one and somehow can't get a new one while clients are on a new one, then reachability issues might arise. However, this is a situation we already have at the moment since the service will simply not work if it doesn't have a live consensus while a client has one.

Fixes #40237 (closed)

Signed-off-by: David Goulet dgoulet@torproject.org