Split the `ty_python_semantic` into more crates

[MichaReiser]

The ty_python_semantic crates has become pretty big and slow to compile. Splitting the type inference logic is tricky but we could try:

• Extract the module resolver into ty_module_resolver:
  • Create a new Db in the resolver crate with a search_paths method (to remove the dependency on Program)
  • Create a new TestDb for the module resolver
  • Create a SearchPathBuilder to replace Program::from_settings.
  • I'm sure there are some more wrinkles to it
• Extract ty_python_infer for the type inference logic. This seems much trickier. Not sure if it's worth it