Discontinue support for building the kapitan binary

[ramaro]

Describe the bug/feature
Building the kapitan binary has historically taken a lot of effort to maintain and it's becoming extremely time consuming get it to work at this stage.
I have low visibility on the actual user base of the binary but suspect it is very small (please shout if you use it!)

I propose the removal of the kapitan binary from the main project.

Instead we should:

• Create a new project to track kapitan and build the binary
• Alternatively build "python executables" using Pex, Shiv or others
• Keep building and updating the docker image

[ramaro]

done in #741