default impls of width_for_height,hfw should chain directly not use wrapper API

default impls of width_for_height,hfw should chain directly not use wrapper API

In GtkBin and GtkWidget we tried to provide handy defaults that
call get_width if there's no get_width_for_height and
get_height for get_height_for_width.

However, they used the wrapper API on GtkSizeRequest instead of
chaining directly to the other method implementation.

This could result in all kinds of surprising behavior, for example,
get_width_for_height() would now already include the effects of set_size_request().

If nothing else it's inefficient. But it's just conceptually wrong,
because to chain to another implementation, we should call the other
implementation, not call a wrapper around the other implementation
(when we're already inside a previous invocation of the wrapper,
i.e. compute_size_for_orientation() ends up reinvoking itself
in the same orientation on the same object which it pretty
likely isn't intending to do)

https://bugzilla.gnome.org/show_bug.cgi?id=628829