Get rid of the individual example functions, as they are not really independent from one another anyways (given that they use absolute subplot positioning onto the main figure). This also allows not having to reload the sample data in each function, and thus concentrate more on showcasing the ImageGrid functionality.

Group some kwargs to ImageGrid in a single line; e.g. the cbar arguments clearly logically belong together.

Inspired by the point about example length at https://discourse.matplotlib.org/t/new-approach-to-matplotlib-example-galleries/23359.

PR Summary

PR Checklist

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• New plotting related features are documented with examples.

Release Notes

• New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst