For the first pass, we can introduce a new Helm variable to define the different installation stages.

# same as `linkerd install config`
helm install --name linkerd --set Stage=config charts/linkerd2

# same as `linkerd install control-plane`
helm install --name linkerd --set Stage=control-plane charts/linkerd2

In future iterations, we can consider exploring using tags and conditions to include different subcharts based on the installation stage.

The behaviour of the existing linkerd install config and linkerd install control-plane should remain unaltered.

cc @grampelberg