[NEW][Features] Added support override data of ChoiceType

[salkhwlani]

sometimes maybe need to override choices the field with advanced logic, I know there is query_builder for Entity but its limit for a query & data from the database, but now can override data of all fields they base of ChoiceType field

Also, added simple test unit for this PR

example for using with Entity field

        $this->add('languages', 'entity', [
            'class' => 'App\Language',
            'data_override' => function ($choices, $field) {
                $choices['testID’] = 'test';
                return $choices;
            }
        ]);

[kristijanhusak]

Looks good, thanks!