Use two step creation of wxListHeaderWindow to avoid reentrancy under OSX.

This improves the solution of the problem already solved in r74197 by
separating setting of m_headerWin variable from the window creation instead of
using an explicit recursion check.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74231 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Check wxListCtrl::GetItemRect() origin in the unit tests.

Verify that the top item is _not_ at (0, 0) when the header is present in the
control, as the control client coordinates should not take the header into
account.

This test passes when using wxGenericListCtrl since r74197, add it to ensure
that it doesn't get broken again later.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74232 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Remove the unused code instead of commenting it out.

Just clean up the fixes of r74197.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74233 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775