Run mdbook tests on Hydroflow+ docs

[shadaj]

Not sure how feasible this actually is given that Stageleft is involved, but we need some solution to ensure that the docs aren't out of date. Maybe we should pull the snippets directly from Rust files or something.

[MingweiSamuel]

Maybe we should pull the snippets directly from Rust files or something.

Yeah I set up some stuff for this for the hydroflow quickstart examples

https://github.com/hydro-project/hydroflow/blob/4bdd5568fa0a6674f650f91a029fab302cbf14f4/docs/docs/hydroflow/quickstart/example_5_reachability.mdx#L55-L67

[MingweiSamuel]

(half completed in #1318)

[shadaj]

Infra set up in #1592, we inline documentation as doctests to ensure they compile.