Cleanup: CMake: Modernize bf_bmesh dependencies

Pretty straightforward

- Remove any bf_bmesh paths from INC
- Add a dependency though LIB when missing

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

Pull Request: https://projects.blender.org/blender/blender/pulls/132203

source/blender/python/mathutils/CMakeLists.txt

@@ -5,7 +5,6 @@
 set(INC
   .
   ../../blenkernel
-  ../../bmesh
   ../../imbuf
 )
 
@@ -41,6 +40,7 @@ set(SRC
 
 set(LIB
   PRIVATE bf::blenlib
+  PRIVATE bf::bmesh
   PRIVATE bf::depsgraph
   PRIVATE bf::dna
   bf_imbuf