Refactor artifactInfos handling after rebasing

[philippotto]

• the name could be better? should we narrow it down to be proofreading/mesh specific since this is the only thing currently contained?
• maybe it should just be a function that can be invoked instead of passing its parameters to resolveApplyingUpdateArtifacts?
• should it even be returned in reapplyUpdateActionsFromSaveQueue when it's not used?