Replace Redis with Valkey

[aldy505]

Caution

This is me playing around with Valkey as a Redis replacement, since so many people from the community mentioned Valkey already.
There is no guarantee that this will be merged at all.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.45%. Comparing base (e4d311b) to head (89d2ed9).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3868   +/-   ##
=======================================
  Coverage   99.45%   99.45%           
=======================================
  Files           3        3           
  Lines         183      183           
=======================================
  Hits          182      182           
  Misses          1        1           

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[hubertdeng123]

It's nice to experiment with this, but could cause some pain for us to maintain self-hosted since prod uses redis

[frederikspang]

While valkey is a great replacement - I think Redis 8 should be the natural next-step - We're running redis:8.0.2-alpine in prod; And we're seeing no problems there. We could try tuning for io-threads for throughput?

I haven't measured how much throughput is actually in Redis, by default (vs kafka vs postgresql for instance).

But if Celery + rate limits + something-else is running there, there must be some.

I can test out 8.2 with increased io-threads over the next few weeks in our prod.