[dagit] Give Sensors and Schedules unique IDs

Summary: Current IDs for Schedules and Sensors are not properly unique across repos, since they just glue together the schedule/sensor name and the pipeline name, both of which can be repeated in separate repos. This causes problems for Apollo caching.

Test Plan: Buildkite. Run Dagit, inspect Apollo cache, verify presence of new IDs.

Reviewers: yuhan, alangenfeld, dgibson

Reviewed By: alangenfeld

Differential Revision: https://dagster.phacility.com/D8644