[Charts] Allow configuring redis instance for trace chunks

What does this MR do?

This allows configuring a traceChunks redis instance in kubernetes

Related issues

Part of gitlab-com/gl-infra/scalability#1094 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

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

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes in combination with: gitlab-com/gl-infra/scalability#1095 (closed) this new Redis instance would be accessible from GitLab-rails
• Documentation created/updated: The use of this extra Redis instance will be documented once we add the functionality in gitlab-com/gl-infra/scalability#1095 (closed)
• [-] Integration tests added to GitLab QA: This redis instance isn't used yet, but will be in: gitlab-com/gl-infra/scalability#1095 (closed) which will contain tests

• Equivalent MR/issue for omnibus-gitlab opened: gitlab-org/omnibus-gitlab!5316 (merged)