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We're not using these synchronously so we can buffer them a bit to avoid
blocking quite as much.

This also combines all incoming channels into a single one to ensure all
operations are processed in-order. This might be overkill bit it makes reasoning
about this a bit simpler.

Fix: don't ignore received blocks for pending wants

Test: fix flakey session peer manager tests

Refactor: use global pubsub notifier

ci: allow circle to use any orb version

ci: fix badge and orb cache

ci: finish circleci migration