hs-v3: Turns out the hs_ident circuit_type is not used

I stumble upon this while investigating #30200 (moved). My HS debugging showed up with circuit type set to INTRO for a rendezvous circuit.

In, one of the most insane function we have, circuit_get_open_circ_or_launch(), towards the end, we set the HS identifier of the open circuit:

          circ->hs_ident =
            hs_ident_circuit_new(&edge_conn->hs_ident->identity_pk,
                                 HS_IDENT_CIRCUIT_INTRO);

... notice, we only use INTRO type, never the RENDEZVOUS one.

Further looking at it, it appears that the hs_ident->circuit_type field is just pointless. Client will only set the INTRO (see code above) and the service will properly set both. But then after that, it is just never used.

I propose we either remove it or fix the client side because if we ever rely on that field, it is of today really wrong client side.