Conduit column.search: add status, sequence and isDefault to API results

Summary:
This seems like a fairly obvious oversight with the column.search API.

Knowing:

1. isHidden - boolean to indicate Active vs Archived
2. isDefaultColumn - the one that Tasks get dropped in by default, usually called "Backlog"
3. sequence - numerical order on the Workboard

are all necessary for a lot of things that very sensible real-world API clients need to do when working with columns.

Partial cherry-pick from:

https://phabricator.wikimedia.org/rPHABebfe30890b52784d222ec4ed36c05462b2a57f92

Closes T15484

Test Plan:
Tested on phabricator.wikimedia.org over many months and used by real client apps.

To do additional tests, visit this page:

/conduit/method/project.column.search/

Check that the new fields are returned correctly and nothing explodes.

Reviewers: #blessed_committers, O1 Blessed Committers, 0, avivey, valerio.bozzolan

Reviewed By: #blessed_committers, O1 Blessed Committers, 0, valerio.bozzolan

Subscribers: Cigaryno, 0, speck, tobiaswiese, valerio.bozzolan, Matthew

Maniphest Tasks: T15081, T15484

Differential Revision: https://we.phorge.it/D25038