bpo-32030: Rewrite _PyMainInterpreterConfig (#4854)

_PyMainInterpreterConfig now contains Python objects, whereas
_PyCoreConfig contains wchar_t* strings.

Core config:

* Rename _PyMainInterpreterConfig_ReadEnv() to _PyCoreConfig_ReadEnv()
* Move 3 strings from _PyMainInterpreterConfig to _PyCoreConfig:
  module_search_path_env, home, program_name.
* Add _PyCoreConfig_Clear()
* _PyPathConfig_Calculate() now takes core config rather than main
  config
* _PyMainInterpreterConfig_Read() now requires also a core config

Main config:

* Add _PyMainInterpreterConfig.module_search_path: sys.path list
* Add _PyMainInterpreterConfig.argv: sys.argv list
* _PyMainInterpreterConfig_Read() now computes module_search_path
diff --git a/Include/internal/pystate.h b/Include/internal/pystate.h
index 6b527fb..305526d 100644
--- a/Include/internal/pystate.h
+++ b/Include/internal/pystate.h
@@ -61,7 +61,7 @@
 
 PyAPI_FUNC(_PyInitError) _PyPathConfig_Calculate(
     _PyPathConfig *config,
-    const _PyMainInterpreterConfig *main_config);
+    const _PyCoreConfig *core_config);
 PyAPI_FUNC(void) _PyPathConfig_Clear(_PyPathConfig *config);