Add GraphQL endpoints to list how many jobs are pending and running

Release notes

Problem to solve

As an admin of a self hosted runner fleet, I want to know how many jobs are pending/running programmatically, so I can autoscale runners more effectively.

Currently I can use the Jobs REST API but want to get it via GraphQL too.

Proposal

• Add a GraphQL endpoint to list current number of jobs running for a pipeline/project
• Add a GraphQL endpoint to list the current number of jobs pending for a pipeline/project
• More metadata may be required to fulfill the user story

Intended users

Metrics