[dagit] Schedule permalink
Create a permalink page for individual schedules, with metadata and recent runs for that schedule.
View individual schedule, verify proper rendering and behavior.
- Toggle schedule on/off, verify success
- View config dialog
- Navigate to playground
Reviewers: dgibson, johann, prha, bengotow
Reviewed By: dgibson
Differential Revision: https://dagster.phacility.com/D5165