Instead of preloading the status, we now preload the
latest pipelines instead for each commit. This gives us more
flexibility on how to display the status.

This also helps us avoid passing the current_user deep through
the model methods. Best to call the detailed_status in the
view/presentation layer.

We also extracted commit's pipeline behavior into its own class.
This is to better isolate and organize the pipeline related behavior
of the Commit object.

Moving the pipeline behavior into its own class resulted
to a lot of breaking changes though. So instead of always having to
create your own instance of a CommitWithPipeline, we're just gonna
use the same commit object but just delegate the pipeline related
calls to the CommitWithPipeline instance.