[bitnami/redis-cluster] add support to disable persistence and add custom config

[anessi]

Description of the change

• Adds support to disable persistence (uses emptyDir instead of a PVC). This is required if one wants to use Redis with in-memory data only. It makes sense to disable AOF and RDB persistence in the config in that case.

    # Disable AOF and RDB persistence as we keep everything in memory only, see https://redis.io/topics/persistence
    appendonly no
    # Disable RDB persistence, AOF persistence already disabled above.
    save ""

• Adds support to supply a custom Redis configuration, e.g. to support an older version of Redis. With the current setup the config is hard-coded and not backwards compatible, so the current chart version can't be used with an older version or Redis.

Benefits

Adds additional features already covered, e.g. in the bitnami/redis chart. Does not change the default behavior and the changes are fully backwards compatible.

Possible drawbacks

Additional complexity

Applicable issues

• fixes charts/redis-cluster disable persistence #4484
• fixes Make redis-cluster chart backwards compatible for Redis 6 (not only Redis 7) #13409

Checklist

• Chart version bumped in Chart.yaml according to semver. This is not necessary when the changes only affect README.md files.
• Variables are documented in the values.yaml and added to the README.md using readme-generator-for-helm
• Title of the pull request follows this pattern [bitnami/<name_of_the_chart>] Descriptive title
• All commits signed off and in agreement of Developer Certificate of Origin (DCO)

[marcosbc]

LGTM! Thanks for the contribution!