hs: Fix ADD_ONION with client authorization

Turns out that passing client authorization keys to ADD_ONION for v3 was not working because we were not setting the "is_client_auth_enabled" flag to true once the clients were configured. This lead to the descriptor being encoded without the clients.

This patch removes that flag and instead adds an inline function that can be used to check if a given service has client authorization enabled.

This will be much less error prone of needing to keep in sync the client list and a flag instead.

Fixes #40378 (closed)

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