Don't enable dialog navigation inside wxFrame by default.

Don't enable dialog navigation inside wxFrame by default.

This was done, apparently accidentally, by r68366 and resulted in cursor arrow
keys not being sent by default to the wxFrame children under MSW any more as
they were used for dialog navigation instead.

So don't derive wxTopLevelWindow from wxNavigationEnabled<> any more and only
derive from it at wxDialog level.

Closes #15445.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74722 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775