Cleanup: move motion paths into editors/animation

Having this in blenkernel caused bad level calls to bf_editors_anim,
causing tests that use 'blenkernel' to require almost all libraries.
(complicating gtest linking & causing large binaries).

source/blender/python/intern/CMakeLists.txt

@@ -118,6 +118,7 @@ set(SRC
 )
 
 set(LIB
+	bf_editor_animation
 	bf_editor_interface
 	bf_editor_space_api
 	bf_python_gpu