Add a legend to the deployment visualization

Based on the #32266 (comment 239824054), we should add a legend to the current deployment visualization page. The legend should have the following states (Succeeded, Running, Failed, Pending, Unknown)

Essentially, we are adding just the circled legend to the current Deployments visualization on the Environments page, as a first step towards creating an Infrastructure Dashboard: This issue does not implement the visualization dropdown (as seen in the mockup)

As part of this work, we will also update the colors of the deployment visualization to be more accessible:

All of the hex values for these colors are available in the measure spec.