Add support for Mariner distroless images

[tofay]

What would you like to be added:
syft can identify RPM packages in Mariner's distroless container image

Why is this needed:
Enable scanning and subsequent CVE checking of Mariner distroless images

Additional context:
Mariner produces distroless images similar to https://github.com/GoogleContainerTools/distroless but containing Mariner packages.
These images don't contain a full RPM database, but they do contain a manifest file detailing the RPMs in the image. https://github.com/microsoft/CBL-Mariner/blob/main/toolkit/docs/how_it_works/5_misc.md#rpm-manifest-file

Syft could read this to determine the contained RPM. syft wouldn't be able to extract as much information as it could from an RPM db, e.g per-file data is not present, but it could extract enough information to enable subsequent CVE checking.