This is unfortunately massive but both functionalities were extremely
intertwined and it would have required us to actually change the HSv2 code in
order to be able to split this into multiple commits.

After this commit, there are still artefacts of v2 in the code but there is no
more support for service, intro point and HSDir.

The v2 support for rendezvous circuit is still available since that code is
the same for the v3 and we will leave it in so if a client is able to
rendezvous on v2 then it can still transfer traffic. Once the entire network
has moved away from v2, we can remove v2 rendezvous point support.

Related to #40266

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