Add support for output per pipeline step

[zbal]

Currently only the step result (return code) is propagated from step to step.

We need a way to capture / consume the output from step to step (eg. text, json, etc.)

We have the task run folder in the workspace pipelines folder where we typically capture the logs, we could extend its use to include the output of the task. That output could be more than just stdout/stderr and be some formatted messaged...

Shall each step create a {step_id}.json file in the task run folder ? and be consumable by the next steps by addressing something like step.{id}.data ? that json file could be parsed to offer attribute access.

/cc @JuhaS