Make wxDataViewCtrl::GetColumnPosition() return the index under MSW as per GTK and...

Make wxDataViewCtrl::GetColumnPosition() return the index under MSW as per GTK and the docs (fixes #12129), give immediate visual feedback after calling e.g. wxDataViewColumn::SetHidden(true) under MSW, also per GTK+ and as I'd expect. Make GTK+ control emit header click events also for non-reorderable columns. Add a few tests for wxDataViewColumn::SetHidden() and wxDataViewCtrl::GetColumnPosition()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64549 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775