Cleanup: CMake: Modernize bf_blenkernel dependencies

Pretty straightforward

- Remove any blenkernel paths from INC
- Add a dependency though LIB

context: https://devtalk.blender.org/t/cmake-cleanup/30260

Pull Request: https://projects.blender.org/blender/blender/pulls/109939

source/blender/python/mathutils/CMakeLists.txt

@@ -4,7 +4,6 @@
 
 set(INC
   .
-  ../../blenkernel
   ../../bmesh
   ../../depsgraph
   ../../imbuf
@@ -41,6 +40,7 @@ set(SRC
 )
 
 set(LIB
+  PRIVATE bf::blenkernel
   PRIVATE bf::blenlib
   PRIVATE bf::dna
   bf_imbuf