Fix setting tooltips for wxSearchCtrl and other composite controls.

Fix setting tooltips for wxSearchCtrl and other composite controls.

Propagate SetToolTip() call on wxCompositeWindow to all subwindows to ensure
that the tooltip is shown for all parts of the window.

Notice that this is still not ideal as the tooltip temporarily disappears when
mouse moves from one subwindow to another, instead of staying in place as it
does with "monolithic" windows and ideally we should find a way to avoid it
(should be possible at least under MSW with TTM_RELAYEVENT) but for now this
is already much better than nothing.

Closes #13523.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@69286 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775