This rejiggers some stuff in the main completions entrypoint
in `ty_ide`. A more refined `Completion` type is defined
with more information. In particular, to support auto-import,
we now include a module name and an "edit" for inserting an
import.
This also rolls the old "detailed completion" into the new
completion type. Previously, we were relying on the completion
type for `ty_python_semantic`. But `ty_ide` is really the code
that owns completions.
Note that this code doesn't build as-is. The next commit will
add the importer used here in `add_unimported_completions`.
bcc8d6910b