[dagit] Tag truncation on Playground

Summary:
Repair long tags on the Playground view by setting a max-width. Overflow should render an ellipsis.

I also did some tidying around how the tags are rendered, including using blueprint colors and fixing some flex issues.

Test Plan:
View Playground, add some tags including very long tags. Verify correct rendering. Shrink window horizontally, verify proper wrapping behavior.

View Runs page, verify same.

Reviewers: bengotow, catherinewu, prha, sashank

Reviewed By: prha

Differential Revision: https://dagster.phacility.com/D4864