Removal: Package pipelines in API payload should be paginated

Problem

A request to the API for /api/v4/projects/:id/packages will return a paginated result of packages, but each package will list all of it's pipelines in this response.

We've seen that there are cases where the number of pipelines may be in the hundreds, or possibly exceed 1000.

This is a ~performance concern

Solution

We should remove pipelines from the response. This is a breaking change and can only occur in a major release, so we will plan on making this update in %15.0.

The pipelines field should return an empty array (constant value).

#341950 (closed) proposes adding a separate REST API to handle paginated pipelines for a given package, but it is worth noting pagination is already available via GraphQL.