Lint: multiple factory definitions that make the same object

Idea for a lint: complain if two factory definitions create the same object. This is a goal towards these ideals:

• each factory definition is the minimum required to make the object
• anything additional is added via traits

We'll need to consider factories that make e.g. Hash, String, Array -- either by letting the user turn off the linter for them, or by recognizing them as OK.

The issue names no files, tests, or entry points. Start by locating the project's existing lint implementation and how factory definitions are represented, then determine how duplicate created objects and exceptions such as Hash, String, and Array should be handled. Done means the lint detects redundant factory definitions with a documented way to allow intentional cases.