docs(autonomi): refactor documentation for API

[b-zee]

• Remove data feature, as it is the basic feature needed for the API to function.
• Add top-level crate example docs.
• Move Python and WASM documentation to their own READMEs.
• Annotate feature-gated items so it's clear in the documentation a certain feature has to be enabled to use (e.g. fs).
• Some renames and exposing modifications.