Simplify the code logic of launching HS circuits
The intro/rendezvous parts of circuit_get_open_circ_or_launch()
are very complicated, and then they call circuit_get_open_circ_or_launch()
which is also extremely complicated.
A minimal action item for improving the situation here would be to split the HS-parts of connection_ap_handshake_attach_circuit()
which are already pretty disentangled into their own function. That's pretty easy to do.
The harder part of this would be to see if we can also split the HS parts of circuit_get_open_circ_or_launch()
in some way.