R1:68b1dee1390d

Replace the "Choose Subtype" radio buttons dialog with a simpler "big stuff you click" sort of UI

Summary:
Ref T13222. Fixes T12588. See PHI683. In several cases, we present the user with a choice between multiple major options: Alamnac service types, Drydock blueprint types, Repository VCS types, Herald rule types, etc.

Today, we generally do this with radio buttons and a "Submit" button. This isn't terrible, but often it means users have to click twice (once on the radio; once on submit) when a single…