Package pipelines API endpoint

## Background When using the [package API](https://docs.gitlab.com/ee/api/packages.html) 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. https://gitlab.com/gitlab-org/gitlab/-/issues/289956 is going to remove this portion of the payload in %15.0 ## :fire_engine: 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](https://docs.gitlab.com/ee/development/database/keyset_pagination.html). Similar to the keyset pagination for other endpoints, subsequent pages can be retrieved using the URL returned in the `Link` header in the response.

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