fix: Idempotent helm installations

[NickLarsenNZ]

Currently stackablectl has the following behaviours:

• Skips applying a rendered chart if it already exists.
• Installs charts using the helm install style of chart installation.

This results in changes to helm values not being applied, or failures when upgrading such as:

❯ stackablectl demo install trino-iceberg
An unrecoverable error occured: demo command error

Caused by these errors (recent errors listed first):
 1: failed to install demo "trino-iceberg"
 2: failed to install stack
 3: failed to install stack manifests
 4: failed to install Helm release minio
 5: failed to install Helm release
 6: release minio (5.0.14) already installed, skipping requested version 5.2.0

It would be nicer to take care of the upgrade by using the idempotent style of chart installation: helm upgrade --install