Create a sqlmesh timeseries metric for dependents

[ryscheng]

What is it?

We want a timeseries metric for dependents (i.e. how many artifacts/projects depend on me?)

The timeseries_events_by_artifact model is copied into a different query processor (e.g. Clickhouse or Trino) for running the sqlmesh pipeline.

Once the ADD_DEPENDENCY events are in the event table, then we should write a sqlmesh model for computing a timeseries metric for new dependents by an artifact (an npm package).

Reuven's sqlmesh metrics factory should auto-rollup by project and by collection if you solve this first https://github.com/opensource-observer/oso/issues/2200