Preload workflows for url generator

The url generator no longer loads workflows one at a time
on demand, they must be pre-loaded to ensure we are not
doing a large number of network round trips while generating
urls.

Bug: 68225
Change-Id: I216ee93a9f9e521d080c946c429defd03a841a0c
(cherry picked from commit 13b2983b925712806c2e2463489db404022d6941)