Prune managed resources when sylva-units-status kustomization is ready

This MR is composed of two commits:

• pruning only when sylva-units-status kustomization is ready

• a refactoring of unit testing adding flux mock to make tests more efficient (may be moved to another MR)

  now to test the pruning of old source, we need:

  • sylva-units-status kustomization to be ready
  • which is tested only if all managed ressources are ready (repos + helm-release)

  This refactoring introduce a mock for flux controller which

  • create the repo artifact (setting revision) and set them ready
  • set the helmrelease ready
  • set the kustomizations ready if the associate source is ready and set LastAppliedRevision to the revision of the source

Related issue: sylva-projects/sylva-core#3310 (closed)