Remove motion Folder from Structure

Description

The motion folder at the base of the Autoware.Auto repo contains the folders control, motion_model, and planning. These would better fit elsewhere.

Expected behavior

The top-level folders in the src folder of Autoware.Auto should represent a single domain, if possible, which directly contains packages without sub-folders. This is not possible for all folders (e.g.

Definition of Done

• The control folder can be moved to the root of src
• The planning folder can be moved to the root of src
• The motion_model folder can be moved to src/common