O1.4 - Measure the number of Tor relays that support IPv6 reachability checks

See Proposal 313: Relay IPv6 Statistics: https://gitweb.torproject.org/torspec.git/tree/proposals/313-relay-ipv6-stats.txt

Tor's IPv6 reachability checks are described in: Proposal 311: Tor Relay IPv6 Reachability: https://gitweb.torproject.org/torspec.git/tree/proposals/311-relay-ipv6-reachability.txt

The child tickets are in proposal section order, but they will probably be implemented in this order:

Dependencies:

• Prop 311: 5. Declare Support for Subprotocol Version "Relay=3" (O1.1, legacy/trac#33226 (moved))

Implementation:

• Write a Script that Counts IPv6 Relays in the Consensus

Metrics Review:

• Check IPv6 Relay Consensus Counts Script

Internal Testing:

• Test IPv6 Relay Consensus Counts using Chutney (O1.3, legacy/trac#33267 (moved))

Public Tor Network Testing:

• Test IPv6 Relay Consensus Counts on the Tor Network

Monitoring:

• Monitor IPv6 Relay Counts in the Consensus

Children:

• #33262 (moved) Prop 313: 3. Write a Script that Counts IPv6 Relays in the Consensus
• trac#33266 Prop 313: 7.2. Show IPv6 Relay Counts on Consensus Health
• #33268 (moved) Prop 313: 8.1. Test IPv6 Relay Consensus Counts on the Tor Network
• trac#33269 Prop 313: 8.1. Check IPv6 Relay Consensus Counts Script
• #33270 (closed) Prop 313: 8.1. Monitor IPv6 Relay Counts in the Consensus