Add a spec that checks for crude oil exceptions

[mabijkerk]

Context

In the new emissions accounting method added in #3444 we add an edge exception case for crude oil mix.

Implemented changes

I had AI write a spec that validates whether all relevant crude oil edges downstream of a final demand mixing node carry the exception group (to prevent missing edges) and that checks it the other way around (to prevent adding irrelevant edges).

I explitictly instructed it to use the Atlas graph builder.

Checklist

• I have tested these changes
• I have updated documentation as needed
• I have tagged the relevant people for review

[kndehaan]

Internally discussed that the work of this spec would still require dev effort in reviewing and modifying. As the crude oil exception is a temporary solution I don't think it's the effort to spend too much additional time on this spec. Therefore closing this issue.