This requires the use of the CachingArrayResolver due to the way
MergeRequest.pipelines is implemented.

This is OK to use since the cardinality of `MergeRequest.pipelines` is
low (collections with more than 20 elements are rare). We need to set
an appropriate max page size though, so we set that here to 500
pipelines for any one MR, which is very conservative, since in
gitlab-org/gitlab> the 99th percentile is 39 pipelines per MR.