Add "owners.search" Conduit API endpoint, with CustomField support
Ref T9964. Adds a new-style "owners.search" endpoint, and an extension for customfields.
Puts enough indirection in place to give us nice, consistent "custom.key" user-facing keys instead of "std:custom:owners:na0shf9a8dfdsafl" junk.
- Searched Owners via API.
- Searched by ID.
- Ordered by custom fields.
- Reviewed API docs.
- Used normal search with ordering.
- Viewed custom field values in search results.
Reviewed By: chad
Maniphest Tasks: T9964
Differential Revision: https://secure.phabricator.com/D14758