bugfix [#23148] "ImportError: __import__ not found" on changing Render FPS

The BGE was getting the namespace dict directly from __main__ which conflicts
with my recent fix to get the pickle module working which to overwrote the __main__ module on script execution.

Simple fix is to have the BGE and Blender use the same method of getting namespaces.
Renamed CreateGlobalDictionary() to bpy_namespace_dict_new() and moved into bpy_internal_import.c

pickle still wont work in the BGE since we make a copy of __main__ namespace but for speed would rather not have to replace the __main__ module many times per second.

source/blender/python/generic/bpy_internal_import.h

@@ -60,5 +60,7 @@ extern PyMethodDef bpy_reload_meth[];
 struct Main *bpy_import_main_get(void);
 void bpy_import_main_set(struct Main *maggie);
 
+/* name namespace function for bpy & bge */
+PyObject *bpy_namespace_dict_new(const char *filename);
 
 #endif				/* EXPP_bpy_import_h */