RETRIEVEMODE=cutout and INTERSECT parameter reintroduction

[Bonnarel]

During Sydney DAL-2 session (https://wiki.ivoa.net/internal/IVOA/InterOpMay2024DAL/DAL-2-notes), Gregory D-F made the comment that if it is to be useful the newly proposed RETRIEVEMODE parameter which allows to choose that the access_url FIELD is containing a direct SODA-like URL to provide a cutout bounded by the query parameters should allow the revival of the SIAV1 INTERSECT=COVERS feature. (https://www.ivoa.net/documents/SIA/20091116/REC-SIA-1.0.html#INTERSECT)

Indeed currently SIAV2 only implement INTERSECT=overlap. This may drive to cases where the actual cutout is much smaller than the ROI.

There are two possible solutions.
1 ) assume that RETRIEVEMODE=cutout implies that actually INTERSECT= COVERS
2 ) Reintroduce explicitly INTERSECT as an SIAV2 parameter and let the user choose what she wants.