bpo-34170: Add Python/coreconfig.c for _PyCoreConfig (GH-8607)

* Add Include/coreconfig.h
* Move config_*() and _PyCoreConfig_*() functions from Modules/main.c
  to a new Python/coreconfig.c file.
* Inline _Py_ReadHashSeed() into config_init_hash_seed()
* Move global configuration variables to coreconfig.c
diff --git a/Include/internal/pystate.h b/Include/internal/pystate.h
index e041d37..ef83af5 100644
--- a/Include/internal/pystate.h
+++ b/Include/internal/pystate.h
@@ -72,6 +72,12 @@
     const _PyCoreConfig *core_config);
 PyAPI_FUNC(void) _PyPathConfig_ClearGlobal(void);
 
+PyAPI_FUNC(void) _Py_wstrlist_clear(
+    int len,
+    wchar_t **list);
+PyAPI_FUNC(wchar_t**) _Py_wstrlist_copy(
+    int len,
+    wchar_t **list);
 PyAPI_FUNC(_PyInitError) _Py_wstrlist_append(
     int *len,
     wchar_t ***list,