activex: expose mouse and keyboard events

Mouse and keyboard events are exposed through signal. It tries to follow the
  "stock event" API [1] as close as possible. It isn't possible to use COleControl helpers
  as the ActiveX component doesn't use MFC.

  fix: #20358

  [1] https://docs.microsoft.com/en-us/cpp/mfc/mfc-activex-controls-adding-stock-events-to-an-activex-control



Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>