Use different GitRepository of sylva-core for kustomize-units and sylva-units
What does this MR do and why?
Use dedicated GitRepository of sylva-core for kustomize-units.
Kustomize-based units shouldn't share the source as sylva-units HelmRelease, otherwise they may be updated in an uncontrolled way when this source is updated.
Additionally, in a distinct commit, remove existing_source option from source definition, as it was only used by management-sylva-units unit. We rely instead on sourceRef that was defined in that unit but not honored before.
Related reference(s)
Edited by Francois Eleouet