derive _OP_ARTIFACT_TYPE from ChalkObj.resourceType

## Description

`ChalkObj.resourceType` is currently a set whereas `_OP_ARTIFACT_TYPE` is a single string value. In some places like a docker container `resourceType` can contain both image and container resources whereas artifact type is only reported as a container. Instead of manually setting the reporting field, we can derive it from the `resourceType` if we use something like `OrderedSet` so that first item in the set is the main artifact type and any subsequent types are supplementary and maybe we can report on them separately.

## Result

Will simplify internal code a bit

Start by tracing where ChalkObj.resourceType and _OP_ARTIFACT_TYPE are defined, assigned, and consumed. Review how Docker resources are represented and identify the existing reporting paths; the refactor is done when artifact type is consistently derived from the ordered resource types and supplementary types can be handled separately.

Written by the indexing model from the issue text.