scope-change option for Diff command

It would be useful to be able to have a new `scope-change` option for the Diff command to examine SBOMs for change in scope (required <-> optional).

1. I think that some SBOM generators are not getting it totally right yet. So this would be a quick way to check that a BOM generated by a new tool version has had an impact.

2. I also want to see when changes in our own project impact optional/required. eg, someone writes a couple of lines of code (defect fix or whatever) and suddenly an optional component becomes a required component.

3. Or the developer cleans up code (but not a POM) and a required component becomes optional.