On Linux and MacOS, loading an `Image` from an `InputStream` is
internally handled via an `ImageDataAtSizeProvider`.

When loading `ImageData` by zoom, this interface requires a proper
implementation of the `getDefaultSize()` or `getImageData(int)` method.
Otherwise an `ImageData` of size 1x1 is returned at 100% zoom, otherwise
`null`.

The tests have been updated to test the loading of an `Image` from an
`InputStream` and to also check the size of the `ImageData` at 100%
zoom.

Closes https://github.com/eclipse-platform/eclipse.platform.swt/issues/3011