[redis-ha] Add dataVolumeOverride and statefulSetSuffix for PVC/StatefulSet name customization

[hardy6413]

What this PR does / why we need it:

Adds two values so you can control what the StatefulSet and its PVCs are named:

• dataVolumeOverride (default data) - renames the /data volume, which is
  also the prefix of the PVC name.
• statefulSetSuffix (default server) - the suffix on the StatefulSet name
  (<fullname>-<statefulSetSuffix>).

Because of that it is possible to have a custom pvc/chart name. Additionally this pr fixes a bug in restore-redis init container. Previously with a hardcoded grep -q 'ha-server-0'. That only works if the
name ends in ha, so it's already broken today for anyone using fullnameOverride
or nameOverride

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• DCO signed
• Chart Version bumped
• Variables are documented in the README.md
• Title of the PR starts with chart name (e.g. [stable/mychartname])