refactor: remove YAML save/load methods for subclasses of BaseStandardPipeline

[ZanSara]

Related Issues

• related to Pipeline Config file string validation is too strict for values in load_from_yaml() #3437

Proposed Changes:

• Remove the save_to_yaml and load_from_yaml methods for BaseStandardPipeline. They were half-baked and easily replaceable with a more meaningful call to standard_pipeline.pipeline.save_to_yaml/Pipeline.load_from_yaml
  • Rationale: the saved/loaded pipeline is a standard Pipeline anyway. No checks are performed at any stage. So one could load an indexing pipeline with ExtractiveQAPipeline.load_from_yaml and obtain an ExctractiveQAPipeline object that behaves like an indexing pipeline.
• Update the documentation in Pipeline.load_from_yaml

How did you test it?

• CI

Notes for the reviewer

• This PR is only vaguely related with the referenced issue. The main rationale is explained in the Proposed Changes section.

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 tests that demonstrate the correct behavior of the change
• I've used the conventional commit convention for my PR title
• I documented my code
• I ran pre-commit hooks and fixed any issue

[bogdankostic]

I think we need to rebase to make the pylint check pass.

[bogdankostic]

LGTM