treewide: Update docs and tutorial

[colluca]

Contributions:

• Update publications
  • Add links
  • Align with IEEE Xplore citation style
  • Reuse publications snippet from README.md in docs
• Fix several cross-references
• Move IP documentation sources to top-level doc folder and add unmaintained warning
• Organize sources in docs/rm/ under a hw and sw subdirectory
• After extensive search for a good JSON schema documentation generator (nothing better than adobe/jsonschema2md was found, and this is also not great), drop JSON schema docs altogether
• Add advanced "Code Optimization" tutorial
• Move base tutorial from target/snitch_cluster/README.md to documentation pages (allows us to use MkDocs admonitions which are not a standard Markdown feature)
• Largely update base tutorial
• Display copy button in all code blocks
• Explicitly exclude sources which are not included in navigation tree (removes known info message)
• Change default AXPY parameters for better trace visualization in tutorial and add ROI specification
• Move schemas from docs to util/clustergen folder

Addresses:

• Add datagen and IPC-based verification tutorials to the documentation #162, added to base tutorial
• Snitch paper link in "Custom Instructions" doc section broken #159
• Fix legacy warnings in make docs target #150, remaining warnings are related to missing type annotations
• Memory map documentation out of date #36, mentioned as unmaintained and potentially outdated
• docs: Add DMA, SSR and FREP usage in the tutorial #24, "Code Optimization" tutorial points to relevant resources
• Fix generated documentation #20