Add the ability to load (build) deps from an artifact ref
Description
Now that !1548 (merged) has landed, we are able to extract all of the build dependencies of artifacts from the proto.
This MR adds support for loading ArtifactElements (and their dependencies) in a similar way to how we load Elements.
In addition to this, bst artifact delete
has been extended to support --deps build
for artifact refs and --deps build/run/all
for element names. Appropriate tests have also been added.
Note to reviewers
For the sake of completeness, we should update all of our existing artifact subcommands to handle --deps
, however I would prefer to do this as a follow up in order to avoid polluting this MR with similar/trivial changes.