Expose Drydock leases via Conduit

Summary:
See T13212 for some context and discussion on this being revived.
See T11694 for original context.

Add a query constraint for lease owners and implement the conduit search method for Drydock leases.

Ref T11694. Fixes T13212.

Test Plan:

• Called the API method from conduit and browsed lease queries from the UI.
• Used the new "ownerPHIDs" constraint via API console.

Reviewers: yelirekim, amckinley

Reviewed By: amckinley

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam, epriestley

Maniphest Tasks: T11694, T13212

Differential Revision: https://secure.phabricator.com/D16594