Create ruff_notebook crate (#7039)

## 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`

crates/ruff_notebook/src/index.rs

@@ -0,0 +1,24 @@
+/// Jupyter Notebook indexing table
+///
+/// When we lint a jupyter notebook, we have to translate the row/column based on
+/// [`ruff_text_size::TextSize`] to jupyter notebook cell/row/column.
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct NotebookIndex {
+    /// Enter a row (1-based), get back the cell (1-based)
+    pub(super) row_to_cell: Vec<u32>,
+    /// Enter a row (1-based), get back the row in cell (1-based)
+    pub(super) row_to_row_in_cell: Vec<u32>,
+}
+
+impl NotebookIndex {
+    /// Returns the cell number (1-based) for the given row (1-based).
+    pub fn cell(&self, row: usize) -> Option<u32> {
+        self.row_to_cell.get(row).copied()
+    }
+
+    /// Returns the row number (1-based) in the cell (1-based) for the
+    /// given row (1-based).
+    pub fn cell_row(&self, row: usize) -> Option<u32> {
+        self.row_to_row_in_cell.get(row).copied()
+    }
+}