Added DoGetClientBestSize() and use it for a couple of controls in wxMSW.

Added DoGetClientBestSize() and use it for a couple of controls in wxMSW.

DoGetClientBestSize() returns the best size of the client area, without
accounting for the border which is done by GetBestSize() itself and
DoGetBorderSize() called from it.

Use DoGetClientBestSize() in wxStaticText (where it was done
insideDoGetBestSize() before) and in wxListBox, to fix its height calculation.

Also use correct height of listbox items as returned by the control itself
instead of trying to guess it.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@61169 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775