Prevent use of the "quality" constraint in the Badge search API

Summary:
Ref T12270. This just drops the constraint for now, rather than dealing with all the typecasting stuff and putting us in a position which will almost certainly require backward compatibility breaks in the future.

Also renames "badges.*" to "badge.*" for consistency (all other methods are singular: token.*, project.*, differential.revision.*, etc).

Test Plan:
Saw "qualities" now "Not Supported", while other constraints continue to work:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12270

Differential Revision: https://secure.phabricator.com/D17487