[dagit] Clarify snapshot ID in Runs table
This diff proposes a few changes to the Runs table:
- Unlink the pipeline name. This seems to be a point of confusion, where people want to click to the run itself, but instead click the pipeline name and end up on the pipeline instead.
- Add a column that shows the snapshot ID for the run, linked to the snapshot -- this is the same href as the current pipeline name link, but aims to be clearer about linking to a snapshot.
- Display a "historical" tag for historical snapshots, indicating when a run belongs to a stale pipeline snapshot.
Test Plan: View Runs page, verify behavior described above.
Reviewers: bengotow, alangenfeld, catherinewu, prha, sashank
Reviewed By: bengotow
Differential Revision: https://dagster.phacility.com/D4705