Output the salt states for a specific server

Summary:
Call state.show_sls and state.show_top to provie a JSON document
with the list of states for the current machine.

The new make target allows to publish it in a canonical URL
/datasources/infra/all-states.json.

Test Plan:
https://windriver.nasqueron.org/datasources/infra/all-states.json

Ref T1691

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1691

Differential Revision: https://devcentral.nasqueron.org/D2555