Add flag for whether an OR conn "counts" for bootstrap tracking

We set this flag if we've launched the connection in order to
satisfy an origin circuit, or when we decide the connection _would_
satisfy an origin circuit.  These are the only or_connections we
want to consider for bootstrapping: other or_connections are opened
because of client EXTEND requests, and they may succeed or fail
because of the clients' confusion or misconfiguration.

Closes #25061.