bpo-32030: Add _PyPathConfig_Init() (#4551)

* Add _PyPathConfig_Init() and _PyPathConfig_Fini()
* Remove _Py_GetPathWithConfig()
* _PyPathConfig_Init() returns _PyInitError to allow to handle errors
  properly
* Add pathconfig_clear()
* Windows calculate_path_impl(): replace Py_FatalError() with
  _PyInitError
* Py_FinalizeEx() now calls _PyPathConfig_Fini() to release memory
* Fix _Py_InitializeMainInterpreter() regression: don't initialize
  path config if _disable_importlib is false
* PyPathConfig now uses dynamically allocated memory

Author: vstinner

Include/pylifecycle.h

@@ -103,8 +103,9 @@ PyAPI_FUNC(wchar_t *) Py_GetPrefix(void);
 PyAPI_FUNC(wchar_t *) Py_GetExecPrefix(void);
 PyAPI_FUNC(wchar_t *) Py_GetPath(void);
 #ifdef Py_BUILD_CORE
-PyAPI_FUNC(wchar_t *) _Py_GetPathWithConfig(
-    const _PyMainInterpreterConfig *config);
+PyAPI_FUNC(_PyInitError) _PyPathConfig_Init(
+    const _PyMainInterpreterConfig *main_config);
+PyAPI_FUNC(void) _PyPathConfig_Fini(void);
 #endif
 PyAPI_FUNC(void)      Py_SetPath(const wchar_t *);
 #ifdef MS_WINDOWS