Add additional bucket for CI queue duration

We are currently seeing queues longer than 15 minutes due to the cron job scheduling system. (Runs every hour, and adds all jobs for the hour at once.)

We are pretty reliably hitting this limit on GitLab.com, which makes it hard to distinguish between this issue and more substantive ones.

We should consider adding another set of buckets:

• 30m
• Longer than 30m