[Sources] Expose metadata of resources found on IConformanceSource #421
Description
There's a usecase (e.g. Forge) to know more about the resources managed by a conformance source than just the canonical - which is what the current sources give.
A solution would be to expose the (currently internal ScanInformation) as an interface (or set of interfaces depending on the specific subtype of scaninformation).
The ScanInformation should also be returned for "failing" resources (e.g. resources that do not parse, files that contain gifs in a DirectorySource etc) - the metadata will make clear that the record is not "active" and possibly contain a description of the error why this is the case.
Similarly, when a source finds records with duplicate canonicals, it may flag one as active (as determined, for example using #393) and also report about the rest.
This will facilitate reporting useful debug-information to the user.