[feat] Option for subPath in persistentVolumeClaim volumes

[Fran-Rg]

Is your feature request related to a problem? Please describe.
I would like to share a PVC between clickhouse and postgres (as dependencies of plausible). For that I'm interested in splitting each DB volume path under their own directory

Describe the solution you'd like

            {{- if eq (include "base.persistence.enabled" . ) "true" }}
            - name: {{ include "base.persistence.suffix" (include "clickhouse.fullname" . ) }}
              mountPath: {{ .Values.persistentVolumeClaim.mountPath }}
-->           subPath: {{ .Values.persistentVolumeClaim.subPath }}
            {{- end }}

with .Values.persistentVolumeClaim.subPath: "" in values.yaml

https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.28/#volumemount-v1-core

Describe alternatives you've considered
2 PVCs