Use the same logic in "bin/drydock lease" and LeaseUpdateWorker to identify candidate blueprints
Ref T13676. Currently, "bin/drydock lease" just creates a lease that permits any blueprint.
To prepare for "use specific blueprint X", unify the logic between this workflow and LeaseUpdateWorker so we select only blueprints which at least have coarse compatibility (e.g., if we're leasing a host, only select enabled blueprints of classes that can allocate hosts).
Test Plan: Used bin/drydock lease to try to lease a nonsense type, got sensible error. Leased a host.
Subscribers: yelirekim, PHID-OPKG-gm6ozazyms6q6i22gyam
Maniphest Tasks: T13676
Differential Revision: https://secure.phabricator.com/D21801