[red-knot] Migrate CLI to Salsa

[MichaReiser]

Summary

Still very much in process.

This PR updates the red-knot CLI to use the new Salsa based semantic model.

What's missing:

• Eager scheduling of dependencies for concurrent analysis
• Handling file system changes

Test Plan

[crates/red_knot/src/main.rs:173:21] diagnostics = [
    "Unresolved import 'Base1'",
    "Method A.foo is decorated with `typing.override` but does not override any base class method",
]