treat Py_Finalize() more like MPI_Finalize()

this is done by
- not automatically calling Py_Finalize() when destructing a python interpreter
- adding wrapper functions so that the call to Py_Finalize() is hidden
  and skipped if Python support is no included.
- call the Python::finalize() wrapper in main.cpp (similar to the equivalent Kokkos function)
- add a wrapper of that call to the C library interface

src/main.cpp

@@ -15,6 +15,8 @@
 
 #include "accelerator_kokkos.h"
 #include "input.h"
+#include "lmppython.h"
+
 #if defined(LAMMPS_EXCEPTIONS)
 #include "exceptions.h"
 #endif
@@ -79,15 +81,18 @@ int main(int argc, char **argv)
     delete lammps;
   } catch (LAMMPSAbortException &ae) {
     KokkosLMP::finalize();
+    Python::finalize();
     MPI_Abort(ae.universe, 1);
   } catch (LAMMPSException &e) {
     KokkosLMP::finalize();
+    Python::finalize();
     MPI_Barrier(lammps_comm);
     MPI_Finalize();
     exit(1);
   } catch (fmt::format_error &fe) {
     fprintf(stderr, "fmt::format_error: %s\n", fe.what());
     KokkosLMP::finalize();
+    Python::finalize();
     MPI_Abort(MPI_COMM_WORLD, 1);
     exit(1);
   }
@@ -99,11 +104,13 @@ int main(int argc, char **argv)
   } catch (fmt::format_error &fe) {
     fprintf(stderr, "fmt::format_error: %s\n", fe.what());
     KokkosLMP::finalize();
+    Python::finalize();
     MPI_Abort(MPI_COMM_WORLD, 1);
     exit(1);
   }
 #endif
   KokkosLMP::finalize();
+  Python::finalize();
   MPI_Barrier(lammps_comm);
   MPI_Finalize();
 }