Make clients and bridges send IPv6 extends by default in Tor 0.4.5
If #33818 (moved) is included in Tor 0.4.4, the relays will send IPv6 extends by default. But clients and bridges won't, for anonymity reasons.
By the time 0.4.5 is released, a large number of clients and bridges will be on 0.4.4. So it will be safe for clients and bridge to send IPv6 extends.
Here's what we need to do to change the default:
ExtendByIPv6ORPort=1in the consensus, and
ExtendByIPv6ORPort 1as the default in Tor.
To avoid confusion, clients and bridges will send IPv6 extends, but they won't initiate outbound IPv6 connections to relays. For more details, see #33818 (moved) and ExtendAllowIPv6Addresses.