Change builder to sync style API and remove in-memory working queue

[astefanutti]

Since the build working state is persisted in the cluster with the Build CR, there is no need for an in-memory working queue. Besides, as the builder is reused in pod build strategy synchronous flow,
the API is changed to sync style for ease of use.

[nicolaferraro]

Unrelated, but to solve that volume issue... what about:

• Creating a pod with a init container and a std container
• The init container is the camel k builder that writes data into a emptyDir volume
• The std container is the kaniko pod that pushes the image into the registry

That is independent from the volume used as cache.. Wdyt?

[astefanutti]

That is a very good idea, conceptually better than using a volume for ephemeral data such as build output.

There is still the question of the Kaniko cache that gets warmed in a separated pod, as well as the Maven cache potentially. But these may be considered optional.

[lburgazzoli]

@astefanutti @nicolaferraro is something to be done in this pr or can be done in a dedicated one ?

[astefanutti]

@lburgazzoli it should be done in a dedicated PR.