bpo-36763: Implement the PEP 587 (GH-13592)

* Add a whole new documentation page:
  "Python Initialization Configuration"
* PyWideStringList_Append() return type is now PyStatus,
  instead of int
* PyInterpreterState_New() now calls PyConfig_Clear() if
  PyConfig_InitPythonConfig() fails.
* Rename files:

  * Python/coreconfig.c => Python/initconfig.c
  * Include/cpython/coreconfig.h => Include/cpython/initconfig.h
  * Include/internal/: pycore_coreconfig.h => pycore_initconfig.h

* Rename structures

  * _PyCoreConfig => PyConfig
  * _PyPreConfig => PyPreConfig
  * _PyInitError => PyStatus
  * _PyWstrList => PyWideStringList

* Rename PyConfig fields:

  * use_module_search_paths => module_search_paths_set
  * module_search_path_env => pythonpath_env

* Rename PyStatus field: _func => func
* PyInterpreterState: rename core_config field to config
* Rename macros and functions:

  * _PyCoreConfig_SetArgv() => PyConfig_SetBytesArgv()
  * _PyCoreConfig_SetWideArgv() => PyConfig_SetArgv()
  * _PyCoreConfig_DecodeLocale() => PyConfig_SetBytesString()
  * _PyInitError_Failed() => PyStatus_Exception()
  * _Py_INIT_ERROR_TYPE_xxx enums => _PyStatus_TYPE_xxx
  * _Py_UnixMain() => Py_BytesMain()
  * _Py_ExitInitError() => Py_ExitStatusException()
  * _Py_PreInitializeFromArgs() => Py_PreInitializeFromBytesArgs()
  * _Py_PreInitializeFromWideArgs() => Py_PreInitializeFromArgs()
  * _Py_PreInitialize() => Py_PreInitialize()
  * _Py_RunMain() => Py_RunMain()
  * _Py_InitializeFromConfig() => Py_InitializeFromConfig()
  * _Py_INIT_XXX() => _PyStatus_XXX()
  * _Py_INIT_FAILED() => _PyStatus_EXCEPTION()

* Rename 'err' PyStatus variables to 'status'
* Convert RUN_CODE() macro to config_run_code() static inline function
* Remove functions:

  * _Py_InitializeFromArgs()
  * _Py_InitializeFromWideArgs()
  * _PyInterpreterState_GetCoreConfig()
diff --git a/Include/cpython/pylifecycle.h b/Include/cpython/pylifecycle.h
index ba56664..2f3a0db 100644
--- a/Include/cpython/pylifecycle.h
+++ b/Include/cpython/pylifecycle.h
@@ -14,14 +14,14 @@
 
 /* PEP 432 Multi-phase initialization API (Private while provisional!) */
 
-PyAPI_FUNC(_PyInitError) _Py_PreInitialize(
-    const _PyPreConfig *src_config);
-PyAPI_FUNC(_PyInitError) _Py_PreInitializeFromArgs(
-    const _PyPreConfig *src_config,
+PyAPI_FUNC(PyStatus) Py_PreInitialize(
+    const PyPreConfig *src_config);
+PyAPI_FUNC(PyStatus) Py_PreInitializeFromBytesArgs(
+    const PyPreConfig *src_config,
     Py_ssize_t argc,
     char **argv);
-PyAPI_FUNC(_PyInitError) _Py_PreInitializeFromWideArgs(
-    const _PyPreConfig *src_config,
+PyAPI_FUNC(PyStatus) Py_PreInitializeFromArgs(
+    const PyPreConfig *src_config,
     Py_ssize_t argc,
     wchar_t **argv);
 
@@ -30,22 +30,22 @@
 
 /* Initialization and finalization */
 
-PyAPI_FUNC(_PyInitError) _Py_InitializeFromConfig(
-    const _PyCoreConfig *config);
-PyAPI_FUNC(_PyInitError) _Py_InitializeFromArgs(
-    const _PyCoreConfig *config,
+PyAPI_FUNC(PyStatus) Py_InitializeFromConfig(
+    const PyConfig *config);
+PyAPI_FUNC(PyStatus) _Py_InitializeFromArgs(
+    const PyConfig *config,
     Py_ssize_t argc,
     char * const *argv);
-PyAPI_FUNC(_PyInitError) _Py_InitializeFromWideArgs(
-    const _PyCoreConfig *config,
+PyAPI_FUNC(PyStatus) _Py_InitializeFromWideArgs(
+    const PyConfig *config,
     Py_ssize_t argc,
     wchar_t * const *argv);
-PyAPI_FUNC(_PyInitError) _Py_InitializeMain(void);
+PyAPI_FUNC(PyStatus) _Py_InitializeMain(void);
 
-PyAPI_FUNC(int) _Py_RunMain(void);
+PyAPI_FUNC(int) Py_RunMain(void);
 
 
-PyAPI_FUNC(void) _Py_NO_RETURN _Py_ExitInitError(_PyInitError err);
+PyAPI_FUNC(void) _Py_NO_RETURN Py_ExitStatusException(PyStatus err);
 
 /* Py_PyAtExit is for the atexit module, Py_AtExit is for low-level
  * exit functions.