[dagit] Stop overfetching schedule/sensor in JobMetadata

Summary: I noticed that the schedule and sensor fragments used in JobMetadata are overfetching considerably. Give the switch components their own fragments, since that's all we really need in this circumstance.

Test Plan: View jobs that have schedules and sensors. Verify that they no longer overfetch.

Reviewers: bengotow, prha, sandyryza

Reviewed By: prha

Differential Revision: https://dagster.phacility.com/D9170