Consolidate the 4 gardener charts

[mxmxchere]

Currently we have 4 gardener charts (gardenlet, controlplane, controlplane-runtime, controlplane-application) which are basically the same. try to consolidate in one gardener-chart

[JensAc]

See https://github.com/23technologies/23ke-charts/tree/homogeneous-chart-import
Actually the gardenlet is still a separate chart. However, we could also think of making it a subchart.