Performance issues on displaying external agreement lines

Overview:
In the new agreement lines search, displaying external agreement lines is slow

Steps to Reproduce:

1. Access https://bugfest-nolana.int.aws.folio.org/erm/agreementLines?filters=lineType.type%3D%3Dexternal&sort=name (login erm-admin / erm-admin)
2. See slow to response
3. Examine json returned - includes the 'reference_object' for the entitlement

Expected Results:
In the case of doing an agreement lines search, the reference_object should not be retrieved as this can create large numbers of OkapiLookup calls to eHoldings (https://github.com/folio-org/mod-agreements/blob/master/service/grails-app/domain/org/olf/erm/Entitlement.groovy#L71)

We should avoid this when working from the Agreement lines search
However note that we currently use the same /entitlements endpoint elsewhere where we are retrieving smaller numbers of results - we can change how this works but in any case where we display information from the reference_object we need some way of retrieving the data and displaying in the UI