[Feature] Emit an ArtifactWritten event upon writing an artifact

[QMalcolm]

Housekeeping

• I am a maintainer of dbt-core

Short description

We recently ran into an issue where the run_results.json artifact wasn't being written (#10934). One of the struggles when debugging was whether core was even trying to write out the artifact.

Acceptance criteria

An ArtifactWritten event is emitted whenever an artifact is written

Suggested Tests

Check that when an artifact is written, the associated event is also emitted

Impact to Other Teams

N/A

Will backports be required?

No

Context

No response