Add Gitlab::Redis::TraceChunks instance, attempt 2

What does this MR do?

Follow-up to !63388 (merged). Previous attempt: !62767 (merged). The only new thing compared to the previous attempt is 7e79dc31.

gitlab-com/gl-infra/scalability#1058 (closed)

In gitlab-com/gl-infra&462 (closed) we are working towards using a dedicated Redis instance for CI trace chunk storage. This MR adds a new instance Gitlab::Redis::TraceChunks. There is no code yet that refers to this new instance; that will be added later when we work on gitlab-com/gl-infra/scalability#1095 (closed).

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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Security

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