Send actionable notification whenever something fails in project model

[mkaput]

When something fails in project model code, send a notification to the user instead of just logging an error.

See all TODO comments that look like this one: https://github.com/starkware-libs/cairo/blob/0f0f721f3f9d28f56cc519c4277fde67d0d03934/crates/cairo-lang-language-server/src/lib.rs#L583