Fix drawing of scaled bitmaps in wxCairoContext.

We must offset the coordinate system before scaling it, otherwise incorrect
offset is used.

Add a test for drawing translated/scaled bitmaps to the drawing sample.

See #11097.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@64463 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775