Summary: Per title. Two new server API's: get-healthchecks, and run-healtcheck. Types have all been moved to flipper-common, so that they can be used by doctor, server-core and ui-core packages. Since it were quite some, moved them into a FlipperDoctor namespace.
Reviewed By: nikoant
Differential Revision: D32720510
fbshipit-source-id: 37aa35cde6ebd58479cf0dffec5b7b2da6d22198