backport from main

* rename swig files .i in .swig
* update constraint_solver and routing
* backport math_opt changes
* move dynamic loading to ortools/third_party_solvers

cmake/cpp.cmake

@@ -518,12 +518,12 @@ foreach(SUBPROJECT IN ITEMS
  ${GUROBI_DIR}
  ${PDLP_DIR}
  sat
- xpress
  lp_data
  packing
  scheduling
  set_cover
  port
+ third_party_solvers
  util)
   add_subdirectory(ortools/${SUBPROJECT})
   #target_link_libraries(${PROJECT_NAME} PRIVATE ${PROJECT_NAME}_${SUBPROJECT})