Fallback to `select` if array of `checkboxes` fail

Allows fields that are arrays of strings to be passed to `<select multiple>`
inputs.
Generally speaking, it's a test's job to show mistakes. The more verbose we can be about that, the more useful Formulaic is.

Consider:

```
Formulaic::InputNotFound No select or checkbox has all options in [x, y, z].
```

versus:

```
ActionController::UnpermittedParameters: found unpermitted parameters: letters
```