Add ability to skip plots

This MR adds basic infrastructure to skip plots via the PlotManager.

Additionally, it already implements conditional skipping for MultiversePlotCreator.

Can this MR be accepted?

• Implementation ready
  • Added SkipPlot custom exception
  • Integrated it into PlotManager
  • Added overloadable hook method to BasePlotCreator to check skip conditions
  • Added expected_multiverse_ndim argument to MultiversePlotCreator
• 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 to 0.14.0b0
  • Reviewed & approved by @tgaskin

Related issues

#165 (closed) (not closing, because this is only the infrastructure for it)