Cleanup: use "filepath" term for Main, BlendFileData & FileGlobal

Use "filepath" which is the current convention for naming full paths.

- Main use "name" which isn't obviously a file path.
- BlendFileData & FileGlobal used "filename" which is often
  used for the name component of a path (without the directory).

source/blender/python/intern/bpy_rna_data.c

@@ -177,7 +177,7 @@ static PyObject *bpy_rna_data_temp_data(PyObject *UNUSED(self), PyObject *args,
 
   ret = PyObject_GC_New(BPy_DataContext, &bpy_rna_data_context_Type);
 
-  STRNCPY(ret->filepath, filepath ? filepath : G_MAIN->name);
+  STRNCPY(ret->filepath, filepath ? filepath : G_MAIN->filepath);
 
   return (PyObject *)ret;
 }