[CT-3447] [dbt/artifacts] [spike+] Move RunResultsArtifact to dbt/artifacts directory

[MichelleArk]

Housekeeping

• I am a maintainer of dbt-core

Short description

We'd like to begin moving our ArtifactMixin subclasses upstream of other core modules in order to decouple core's internal functional concerns from external data interfaces. Once the initial structure is laid down in #9193, let's continue this exercise by spiking moving RunResultsArtifact to dbt/artifact. The upstream node classes should be split into data & functional interfaces, defined in dbt/artifacts in dbt/core respectively. Additionally, any inheritance hierarchy for node attributes should be flattened as part of this spike.

Acceptance criteria

A spike report that highlights any potential approaches and their tradeoffs, as well as a summary of any potential blockers encountered.

Impact to Other Teams

N/A - should be a refactor.

Will backports be required?

nope

Context

Should be done after #9193 to avoid duplicating foundational setup work.