Fix HiDPI issues related to image loading

[gyk]

When working on some HiDPI application, I find I have to manually scale the size attribute of nwg_resource for loading Bitmaps/Icons/ImageLists properly. This PR tries to fix it.

[gyk]

Update: In case GetDeviceCaps returns 0, USER_DEFAULT_SCREEN_DPI should be used for DPI instead, as does in https://github.com/microsoft/PowerToys/blob/v0.53.3/src/modules/fancyzones/FancyZonesLib/util.cpp#L130. Otherwise logical_to_physical will panic.