bpo-40226: PyInterpreterState_Delete() deletes pending calls (GH-19436)

bpo-40226: PyInterpreterState_Delete() deletes pending calls (GH-19436)

PyInterpreterState_New() is now responsible to create pending calls,
PyInterpreterState_Delete() now deletes pending calls.

* Rename _PyEval_InitThreads() to _PyEval_InitGIL() and rename
  _PyEval_InitGIL() to _PyEval_FiniGIL().
* _PyEval_InitState() and PyEval_FiniState() now create and delete
  pending calls. _PyEval_InitState() now returns -1 on memory
  allocation failure.
* Add init_interp_create_gil() helper function: code shared by
  Py_NewInterpreter() and Py_InitializeFromConfig().
* init_interp_create_gil() now also calls _PyEval_FiniGIL(),
  _PyEval_InitGIL() and _PyGILState_Init() in subinterpreters, but
  these functions now do nothing when called from a subinterpreter.