[dagit] Add repo location reload to object headers

Summary:
Add a reload button alongside repository names in headers on workspace-level objects. This allows reloading the repository location specific to that object, without needing to care which repository is active in the left nav. Additionally:

• Add a keyboard shortcut, the same as the existing one (alt-R).
• Add text-overflow truncation to the repository name/location, as well as a nowrap style. This will ideally prevent superlong repository names from breaking the UI.
• Tweak some spacing on the schedule and sensor header switch.

Test Plan:
View pipelines, schedules, and sensors in Dagit. Use mouse, keyboard, and shortcut behavior to perform repository location reloads. Verify success.

Use very long repo name strings to try to break the UI. Repeat with minimizing viewport width. Verify that things remain sane.

Reviewers: bengotow

Reviewed By: bengotow

Differential Revision: https://dagster.phacility.com/D6589