Provide option to override traits of generated difference output

[na9da]

Reported in opendatacube slack.

Currently the output layer generated using the difference tool inherits all the traits of the parent item. It should be possible to override some of these traits in the difference item, for example to change the feature info template to something more suited to the difference output.

Test dataset: https://terria-cube.terria.io/#share=s-weAnFnIaphPxgUQRnDa1FftkPom

[na9da]

Fixed by #7243