Enforce a maximum concurrency queue size limit

For #6399 (closed)

From an incident, we notice that some concurrency limit configs on production don't have upper bounds. One good example is InfoRefsUploadPack and similar limits in the same file. They were introduced a long time ago (>6 years ago) without setting a limit.

Surprising, queue bounding by time and length were introduced long afterward. That explains why many of them didn't set the limits to begin with.

This MR enforces default limits for pack-objects limiting and concurrency limits. Those default limits are more than generous. They are greater than any size limits we set on production. It's very unlikely those limits will affect GitLab SaaS or customers. They are helpful in extreme scenarios such as incidents.