Fix using outdated click position in wxAuiTabCtrl mouse handlers, which
resulted in an invalid wxEVT_AUINOTEBOOK_DRAG_MOTION event being
generated and a crash while handling it.
Ensure that we reset m_clickPt when resetting m_isDragging too so that
we don't decide that we're dragging if the mouse enters the window with
the left button already pressed after a previous drag.
See #24027, #24039.
(cherry picked from commit f1a3816cd9da0c3c7ceebe9735d37fb2d3158388)