Update the Makefile after kubebuilder v3 to v4 update

[fabriziosestito]

Is your feature request related to a problem?

The Makefile of this project is a custom version of the Makefile scaffolded by kubebuilder v3.
At the time of writing, this project uses kubebuilder v4.
Also, the Makefile is customized to fit our needs.

This means that:

• Many targets are not needed (such as run, as we are using tilt)
• the help target is not up to date
• starting from the Makefile scaffolded by kubebuilder v4 might be necessary / cleaner
• we might want to rethink the separation between unit and integration tests after Controller restructuring #769
• we want to suggest the contributors to use the tools installed by the Makefile, instead of the system ones, to ensure that the code generation is streamlined

Solution you'd like

Starting from the v4 Makefile as a template, create a slimmed-down version of the Makefile with the targets we need, removing the rest.

Alternatives you've considered

No response

Anything else?

No response

[flavio]

Closing, this has been done in the meanwhile