bpo-36301: Remove _PyCoreConfig.preconfig (GH-12546)

* Replace _PyCoreConfig.preconfig with 3 new fields in _PyCoreConfig:
  isolated, use_environment, dev_mode.
* Add _PyPreCmdline.dev_mode.
* Add _Py_PreInitializeFromPreConfigInPlace().
diff --git a/Include/cpython/pylifecycle.h b/Include/cpython/pylifecycle.h
index 5f3a522..e32e54c 100644
--- a/Include/cpython/pylifecycle.h
+++ b/Include/cpython/pylifecycle.h
@@ -16,7 +16,7 @@
 
 PyAPI_FUNC(_PyInitError) _Py_PreInitialize(void);
 PyAPI_FUNC(_PyInitError) _Py_PreInitializeFromPreConfig(
-    _PyPreConfig *preconfig);
+    const _PyPreConfig *preconfig);
 PyAPI_FUNC(_PyInitError) _Py_PreInitializeFromConfig(
     const _PyCoreConfig *coreconfig);