bpy.utils.fullscreen_3dview and bpy.utils.return_to_previous

bpy.utils.fullscreen_3dview takes a snap shot of the current Blender UI state and sets the 3dview to to fullscreen borderless wth all widgets, overlays, and panels hidden.

bpy.utils.return_to_previous restores Blender UI with the snapshot state when bpy.utils.fullscreen_3dview was called.