Backport BLOCKED_MODULE performance fix from Redis unstable

What does this MR do?

In the context of our Redis 6 upgrade (gitlab-com/gl-infra&395 (closed)) we discovered a performance regression.

This performance regression has now been patched.

In order for us to be able to upgrade redis-sidekiq on gitlab.com to Redis 6.0, we need this fix -- as we're already very close to CPU saturation.

The fix has landed in redis unstable targeting 6.4 and 6.2. It is unclear whether it will land in 6.0, or whether there even will be another 6.0 release.

We may need to maintain this patch until we upgrade to 6.2. But it's a very straight-forward patch. So it may very well be worth it.

Related issues

https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12896

Checklist

See Definition of done.

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Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com
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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for the GitLab Chart opened