Outsource YAML-related functionality to yayaml

This MR removes all functionality from dantro that is now covered by yayaml. Specifically, that is:

• load_yml, write_yml and yaml_dumps
• Error hints and the raise_improved_error_message function

Can this MR be accepted?

• Implementation ready
• Tests added or adjusted
• Documentation extended or updated

• Code quality
  • Changes follow coding guidelines
  • Checked code coverage on new and adjusted code

• Ready for merging
  • Pipeline passes without warnings
  • History cleaned-up or squash option set
  • Changelog entry added
  • Version number bumped