Improve wxBookCtrlBase controller size calculations.

Improve wxBookCtrlBase controller size calculations.

Use GetBest{Height,Width}() in wxBookCtrlBase to compute the controller
control size height/width from its known (from wxBookCtrlBase size itself)
width/height. This will allow to correctly compute the size of wxListCtrl used
by wxListbook once it provides the necessary support for width-from-height and
height-from-width calculations.

See #13898.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71393 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775