Allow workflows to be modified via a YML

[ArBridgeman]

Summary

(more details to be added)
With #686 , we now can access a template in a dictionary-like form. Provided that #683 has been done, we can modify PTB workflows by defining a YML that has a specific format. This tasks are likely to be broken out into smaller pieces.

To Dos

• Define what the YML will look like
  • Use project-keeper as the reference:
    https://github.com/exasol/project-keeper/blob/main/doc/user_guide/user_guide.md
• Set up a pydantic schema to validate
• Create tests to verify schema & loading of the YML
• Modify existing code so that the YML does the specified modifications
• Create tests to verify modifications work as intended
• Significantly update the PTB documentation (main & configuration)