Allow "almanac.service.edit" to create services

Summary:
Depends on D19317. Ref T13120. Ref T12414. See PHI145. See PHI473.

This adds a Conduit-only "type" transaction for Almanac services. This is very similar to the approach in D18849 for Drydock blueprints.

Test Plan:

• Tried to create an empty service via "almanac.service.edit", was told to pick a type.
• Tried to pick a bad type, was told to pick a good type.
• Created a new Almanac service via "almanac.service.edit".
• Tried to edit the service to change the type, wasn't allowed to.
• Created and edited via the web UI, nothing changed from before.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13120, T12414

Differential Revision: https://secure.phabricator.com/D19318