Handle scale factor in another wxMSW wxBitmap ctor taking wxDC

This is similar to db6d565fad (Handle wxDC scale factor in wxBitmap ctor
taking wxDC in wxMSW, 2022-04-10), but for the constructor taking
wxImage and wxDC -- it should also use the DC scale factor, even if it
is not used for scaling the bitmap size in this case.

Add a unit test checking for this.

tests/graphics/bitmap.cpp

@@ -1726,6 +1726,16 @@ TEST_CASE("Bitmap::ScaleFactor", "[bitmap][dc][scale]")
     wxBitmap bmp2(4, 4, dc);
     CHECK( bmp2.GetScaleFactor() == 2 );
     CHECK( bmp2.GetSize() == wxSize(8, 8) );
+
+#ifdef __WXMSW__
+    // A compatible bitmap created from wxImage and this DC should also inherit
+    // the same scale factor, but its size should be still the same as that of
+    // the image.
+    wxImage img(16, 16);
+    wxBitmap bmp3(img, dc);
+    CHECK( bmp3.GetScaleFactor() == 2 );
+    CHECK( bmp3.GetSize() == wxSize(16, 16) );
+#endif // __WXMSW__
 }
 
 #endif // ports with scaled bitmaps support