dri: Try harder to infer the drawable fbconfig if needed

dri: Try harder to infer the drawable fbconfig if needed

This code would work for GLXWindows but not for bare Windows, which I
guess you could argue is a server bug but which we can fix on the client
side with a little effort. We change __glXGetDrawableAttribute to
additionally return false if we failed to find the requested attribute
(which is safe, all the other callers discard the return value). Then
when inferring the fbconfig, if the attribute wasn't found, we ask for
the window attributes to find the visual ID and use that to find the
fbconfig.

Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10381>