Why:
These are essentially internal methods that should not be publicly
available from the base namespace.
One thing worth noticing is that the use of this methods internally was
almost exclusively in the `syntax/default` except for one use on the
`factory_bot/definition`.
Also the deprecation silencing module was referring to the singleton
instance of the ```ActiveRecord::Deprecation``` class and not to the new
deprecation instance that was being used in the ```FactoryBot``` module.
This PR:
- Moves the `trait_by_name` and `register_trait` into the
`FactoryBot::Internal` module
- Deprecates uses of `trait_by_name`, `register_trait` and `traits` from
the `FactoryBot` module.
- Rename DEPRECATOR => Deprecation
This is one of the steps towards fixing [this
issue](https://github.com/thoughtbot/factory_bot/issues/1281)
This PR deprecates the ability to look up a factory based on class instead of symbol.
- The acceptance test `keyed_by_class_spec.rb` tests lookup by class
- Add flag `allow_class_lookup` (default `true`)
- Show a deprecation on class lookup warning when flag is true
- Raise an exception on class lookup when flag is false
- Silence deprecation warnings in tests
Fixes#871
Revert Hound formatting recommendation
