OptionalsimpleSimple applicators just apply subschemas and don't have any validation behavior
of their own. For example, allOf and properties are simple applicators. They
never fail. Only their subschema can fail. anyOf and oneOf are not simple
applicators because they can fail independently of the validation result of
their subschemas.
For non-applicator keywords, this doesn't need to do anything. Just return void.
For applicator keywords, it should call evaluateSchema on each subschema and
return an array with each result.
Used to convert a specific keyword to the normalized format used by the error handlers.