Resolve "For `kind = auto`, respect given layout specifiers"

This MR improves the determine_plot_kind function to account for already-fixed layout encodings. For example, with hue given, kind: auto should never evaluate to pcolormesh, as this would result in errors.

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

Related issues

Closes #231 (closed)