hs-v3: Stop using ip->circuit_established flag
Since #31548 (moved), where we forgot to look if the service intro circuit was established, we rely on ip->circuit_established flag to know if we can use the IP (and in many other places as well).
However, this is a bit of a "duplication" of effort because we have the HS circuitmap that keeps all the intro circuits conveniently indexed by IP auth key.
When a circuit closes or is repurposed, that HS map is cleaned up with hs_circ_cleanup() so regardless what caused the circuit to disappear, our map will always be updated properly.
I believe we should stop relying on the ip->circuit_established flag so in the future we don't get out of sync with the map by mistake or assume state based solely on this flag. The HS map is the only real valid state we should be looking at for HS circuit state.