[Nextcloud] Add useful settings to nextcloud-vars.ini and use helm chart version 3.3.3

The goal is to add in nextcloud-vars.ini all the parameters necessary to choose the database, set Redis (enable/disable and password) and control persistence (Nextcloud installation and database).

This MR also switch to the latest Nextcloud Helm chart (version 3.3.3). The nextcloud-values files has been synced with the upstream values.yaml. Notable change : Cronjob (just need to set enable to true to set it up !) and Prometheus exporter version updated from version 0.5.0 to 0.5.1 and Prometheus Operator ServiceMonitor configuration has been added.

There is also a real update script (the old one just called the deploy one), to avoid launching Minio bucket creation several times.

PS: I can break this MR into three if you prefer.