feat: add pipeline Yaml marshaller

[masci]

Related Issues

• fixes Load/Dump pipelines in Yaml format #6010

Proposed Changes:

We add the following methods to the Pipeline class:

• dumps to return its string representation
• dump to write its string representation to a file-like object passed to the method
• loads to return a Pipeline instance from its string representation
• load to return a Pipeline instance reading its string representation from a file-like object

All the methods can be invoked passing a Marshaller object that will determine what's the string representation format, defaulting to Yaml (the only format available at the moment).

How did you test it?

Unit tests covering the default marshaller.

Notes for the reviewer

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.
• I documented my code
• I ran pre-commit hooks and fixed any issue

[vblagoje]

@masci I also liked this approach. I can't think of a better fit for use of Protocol(s) than (un)marshalling.