* Add basic jupyter notebook support behind a feature flag
* Address review comments
* Rename in separate commit to make both git and clippy happy
* cfg(feature = "jupyter_notebook") another test
* Address more review comments
* Address more review comments
* and clippy and windows
* More review comment
## Summary
This PR moves `Diagnostic`, `DiagnosticKind`, and `Fix` into their own crate, which will enable us to further split up Ruff, since sub-linter crates (which need to implement functions that return `Diagnostic`) can now depend on `ruff_diagnostics` rather than Ruff.
This PR introduces a new `CacheKey` trait for types that can be used as a cache key.
I'm not entirely sure if this is worth the "overhead", but I was surprised to find `HashableHashSet` and got scared when I looked at the time complexity of the `hash` function. These implementations must be extremely slow in hashed collections.
I then searched for usages and quickly realized that only the cache uses these `Hash` implementations, where performance is less sensitive.
This PR introduces a new `CacheKey` trait to communicate the difference between a hash and computing a key for the cache. The new trait can be implemented for types that don't implement `Hash` for performance reasons, and we can define additional constraints on the implementation: For example, we'll want to enforce portability when we add remote caching support. Using a different trait further allows us not to implement it for types without stable identities (e.g. pointers) or use other implementations than the standard hash function.
In ruff-lsp (https://github.com/charliermarsh/ruff-lsp/pull/76) we want to add a "Disable \<rule\> for this line" quickfix. However, finding the correct line into which the `noqa` comment should be inserted is non-trivial (multi-line strings for example).
Ruff already has this info, so expose it in the JSON output for use by ruff-lsp.
