Explain config_type_extended usage and purpose
From #31494 (moved), previously from #30914 (moved):
Make sure that we have a good explanation of CONFIG_TYPE_EXTENDED, how it is used, and how it relates to the type_def pointer.
From #31494 (moved), previously from #30914 (moved):
Make sure that we have a good explanation of CONFIG_TYPE_EXTENDED, how it is used, and how it relates to the type_def pointer.