Add an option to crop the original product to allow fast testing

[alexamici]

At the moment GitHub Actions on simple operation fail with a memory error, apparently due to the large size of the input image, even when opened with blocks.

[jdries]

I would also be interested in this feature: users do not always need the full scene, in some cases they even require a few pixels only. Would be nice to have the ability to process only a specific extent/area of interest.