## Summary
This PR deletes the `DiagnosticKind` type by inlining its three fields
(`name`, `body`, and `suggestion`) into three other diagnostic types:
`Diagnostic`, `DiagnosticMessage`, and `CacheMessage`.
Instead of deferring to an internal `DiagnosticKind`, both `Diagnostic`
and `DiagnosticMessage` now have their own macro-generated `AsRule`
implementations.
This should make both https://github.com/astral-sh/ruff/pull/18051 and
another follow-up PR changing the type of `name` on `CacheMessage`
easier since its type will be able to change separately from
`Diagnostic` and `DiagnosticMessage`.
## Test Plan
Existing tests
## Summary
This PR moves `ruff/jupyter` into its own `ruff_notebook` crate. Beyond
the move itself, there were a few challenges:
1. `ruff_notebook` relies on the source map abstraction. I've moved the
source map into `ruff_diagnostics`, since it doesn't have any
dependencies on its own and is used alongside diagnostics.
2. `ruff_notebook` has a couple tests for end-to-end linting and
autofixing. I had to leave these tests in `ruff` itself.
3. We had code in `ruff/jupyter` that relied on Python lexing, in order
to provide a more targeted error message in the event that a user saves
a `.py` file with a `.ipynb` extension. I removed this in order to avoid
a dependency on the parser, it felt like it wasn't worth retaining just
for that dependency.
## Test Plan
`cargo test`
## 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.
