[FEATURE] Add requirements in Pipeline

[alvarobartt]

Is your feature request related to a problem? Please describe.

Adding a list with the dependencies and their versions within the Pipeline is useful for reproducibility, so ideally we should be able to dump the dependencies used in a Pipeline in both the pipeline.yaml dump, but also to print those when running the Pipeline.

Describe the solution you'd like

Ideally, we should be able to define extra dependencies at Pipeline level, as well as capturing the dependencies of the steps defined within a Pipeline (at least for the ones that we define i.e. not custom ones atm).

Additional context

Related to #573