Feat: Add cluster support for Registry Redis cache

What does this MR do?

This MR introduces redis.cache.cluster params. This was needed as a pre-requisite of gitlab-com/gl-infra/k8s-workloads/gitlab-com!4641 (merged).

The background context is to point registry cache to use redis-cluster-registry instead of redis-registry-cache which in-turn requires upgrading of redis helm chart as currently redis.cache.cluster is not supported.

This is being done as a part of migration of redis-registry-cache to redis-cluster-registry

Related slack conversation: https://gitlab.slack.com/archives/C07U8G0LHEH/p1754398317658019

This MR further solves gitlab-com/gl-infra/k8s-workloads/gitlab-com!4641 (merged)

Issue: gitlab-com/gl-infra/data-access/durability/team#284 (closed)

Epic: gitlab-com/gl-infra/data-access/durability&24

Author checklist

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Required

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• Merge Request Title and Description are up to date, accurate, and descriptive.
• MR targeting the appropriate branch.
• MR has a green pipeline.
• Documentation created/updated.
• Tests added/updated, and test plan for scenarios not covered by automated tests.
• Equivalent MR/issue for omnibus-gitlab opened.

Reviewers checklist

• MR has a green pipeline on https://gitlab.com/gitlab-org/charts/gitlab.
• Consider downstream impact to the Operator, as per evaluating impact from changes to GitLab Chart.