This PR was submitted for the 2.8 branch but it was merged into the 2.7 branch instead (closes#17314).Discussion----------Fix max width for multibyte keys in choice questionFixes wrong key max width for ChoiceQuestion in multibyte stringsBefore:![before](https://cloud.githubusercontent.com/assets/2435655/12203385/977e88c0-b626-11e5-9425-d497f84a9ab3.png)After:![after](https://cloud.githubusercontent.com/assets/2435655/12203390/9d9a0b4e-b626-11e5-8d4e-ba9290820778.png)To replicate you can use this code as an example:```namespace AppBundle\Command;use Symfony\Component\Console\Command\Command;use Symfony\Component\Console\Input\InputInterface;use Symfony\Component\Console\Output\OutputInterface;use Symfony\Component\Console\Question\ChoiceQuestion;class QuesionCommand extends Command{    protected function configure()    {        $this->setName('app:question');        $this->setDescription('Command for testing PR');    }    protected function execute(InputInterface $input, OutputInterface $output)    {        $helper = $this->getHelper('question');        $question = new ChoiceQuestion('Choose something:',            [                'foo' => 'foo',                'żółw' => 'bar',                'łabądź' => 'baz',                'известно' => 'lorem',                'газета' => 'ipsum',            ],            0);        $colour = $helper->ask($input, $output, $question);        $output->writeln('you have chosen: ' . $colour);    }}```| Q             | A| ------------- | ---| Bug fix?      | yes| New feature?  | no| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets |#15368| License       | MIT| Doc PR        | -Commits-------5d2463b Fix max width for multibyte keys in choice question