Jupyter Inspection Framework, Book Theme, and Initial Drafts for Codegen Reference Guides

This MR adds extended interactive inspection functionality and drafts for two reference guides on kernel creation in general, and GPU in particular.

Depends on !429 (merged) .

Inspection Framework

• Start building an interactive inspection framework in pystencils.inspection, to replace the old display_utils.
• Add a feature to the codegen driver to retain and export intermediate results for inspection

Docs Layout and Theme

• Replace furo by sphinx-book-theme
• Expand sidebar structure
• Clean up the logo (it was asymmetric! argh!) and add a separate dark-mode logo

Reference Guides

• Add an installation and setup guide
• Start writing reference guide on kernel creation
• Start writing reference guide on CUDA kernels