Squish Tests: Reset layout

As a developer I would like to verify the following behaviour using Squish:

- Modify the layout.
- Press the `Reset Layout` button.
- Verify that the layout is reset to the default position.

#### Additional info:
Take care to make the test consistent. A useful function to use would be `dragItemBy`, https://doc.qt.io/squish/java-convenience-api.html#java-dragitemby-function. Note that we should try *not* to depend on pixel-offsets in the test if possible, as this will make the test more brittle with respect to resolution changes/SWT updates for example.