kpack hardcodes the lifecycle config map name

[sambhav]

As a part of testing the helm chart release in #686 I realized that kpack currently hardcodes the lifecycle config at https://github.com/pivotal/kpack/blob/ed7fe5056666f0ec1aa4378c92db1d52a0a872c5/cmd/controller/main.go#L160

This makes it hard to provide arbitrary configmap names for it. We can fix this by passing the configmap name through an env var or keep this hardcoded in the helm chart. I think the former might be preferred to avoid conflicts with people accidentally changing this configmap even though the kpack lifecycle image is being tracked through a different config map name.

[tylerphelan]

what if we used a hardcoded label on the configmap instead of its name?