Drop support for `routine` versus `pod` building strategy

[squakez]

The necessity to support the routine building strategy is a kind of a limitation as it requires the operator to be able to manage the operations concerns and the build concern, delegating this to some external Maven processes but on the same running Pod. I think that we should remove the support of routine entirely, letting the operator to spin off a Pod and perform the build accordingly as it already happens with pod strategy. This would simplify the design and maintenance of the project and likely the usage of the operator with one less concern to care. Anyway it would be something to consider in a major release only. Feedback are welcome.