add install for controller-gen and other "gen" tools
add install for controller-gen and other "gen" tools

k8s codegen tools are a bit of a special case; this is explained in a
comment.

Signed-off-by: Ashley Davis <2a98ad09b55d7402451cbad533f334a828c02124@jetstack.io>

cert-manager/cert-manager,jetstack/cert-manager,jetstack/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,cert-manager/cert-manager