[VSA] Add change failure rate (DORA)

Problem

Change failure rate is another key metric of a highly functioning development team: "The percentage of deployments causing a failure in production." Customers are asking for access to this metric.

Once we add #299407 (closed), we should add a new tile to VSA that states the Change failure rate

Proposal

Show Change Failure Rate on the Value Stream Analytics page, measured as Incident count divided by Deployment count.

Note: In a future iteration we could add consideration of Alerts with fingerprints that do not match any incidents to make "failure" detection more robust.

Rough mockup

For 1st iteration this tile should reflect the API tier and remain visible only in GitLab Ultimate