Package pipelines API endpoint

Background

When using the package API to get a single package or list of packages, all pipelines for each package are returned. This is a problem because the pipelines are not paginated and there may be thousands of pipelines for a given package. #289956 (closed) is going to remove this portion of the payload in %15.0

🚒 Solution

Introduce a new rest API endpoint to return paginated results of pipelines for an individual package:

GET /api/v4/projects/<project_id>/packages/<package_id>/pipelines

Offset pagination can be very inefficient when dealing with thousands of records. Therefore we will instead implement keyset pagination.

Similar to the keyset pagination for other endpoints, subsequent pages can be retrieved using the URL returned in the Link header in the response.