Steps needn't necessarily only deal with one build

[kitallis]

Proposal

Our current step model simultaneously feels flexible but is also very rigid at the same time. You can define steps in an "arbitrary" way, but there are various rules attached to it.

One of them is the fact that a Step represents one CI workflow and expects one build artifact to be generated from it.

We should consider making Builds first-class in the system and have them push to various distribution channels as necessary.

This perhaps ties a bit with #94

What this achieves / problem(s) it solves

This reduces the flexibility that normal CI workflows already provide. CI workflows can run multiple builds in parallel, reuse caches, share setup + teardown, push multiple artifacts within a single workflow itself.

We're trading away flexibility and performance on one end for codification and coordination on another.