[dagit] Standardize font-family usage
Standardize our fonts throughout Dagit. Makes things look a lot nicer.
- Use the default font-family supplied by Blueprint, with -apple-system as the primary choice. For recent MacOS versions, this should be San Francisco.
- Define a standard monospace font-family for usage everywhere, Source Code Pro. We use this in some places, but there is a fairly loose mixture of this override and the regular monospace default, which in most cases is sadly Courier New.
Test Plan: View Dagit on latest Chrome, Firefox, Safari on MacOS 10.15.7. Verify that fonts are consistent throughout Dagit.
Reviewers: bengotow, alangenfeld, prha, sashank
Reviewed By: sashank
Differential Revision: https://dagster.phacility.com/D4803