nostrum channel cache repro

Reproduction for bug with Nostrum ~0.9 where channel cache is unpopulated

1. Use elixir & erlang versions as noted in .tool-versions (only really need to care about major/minor versions).
2. Set up NOSTRUM_REPRO_TOKEN environment variable with a test bot account token. (All intents are requested, and message content is required for this test).
3. Run with iex -S mix
4. Run !!repro here on a channel in Discord. Normally this would work but in this case it should spit out an error in logs about no match for the channel in cache.
5. Run !!repro find <channel_id>. This should have the same outcome as above.
6. Run !!repro count. This would be expected to output some number of channels in cache, but instead only outputs 0.

Relevant code in ./lib/repro/consumer.ex.