Add support for existingClaim on persistence

Please support existingClaim in your chart for ALL persistent elements.

As mentionned in #1703 and #5992 (closed) your chart does not support existingClaim to use already created PVC.

Tho both issues got closed due to inactivity.

So i'm making a new issue, asking you to add existing claim to the chart on the differents components :

• Gitaly
• Minio
• Toolbox
• Toolbox Backup

Prometheus, Porgesql and Redis can be used with an existingClaim ad their ar passed to the sub-chart.