bug symfony#28393 [Console] fixed corrupt error output for unknown multibyte short option (downace)

This PR was squashed before being merged into the 2.8 branch (closes symfony#28393).

Discussion
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[Console] fixed corrupt error output for unknown multibyte short option

| Q             | A
| ------------- | ---
| Branch?       | 2.8 <!-- see below -->
| Bug fix?      | yes
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| Fixed tickets | symfony#28320   <!-- #-prefixed issue number(s), if any -->
| License       | MIT
| Doc PR        | - <!-- required for new features -->

[Console] Fixed symfony#28320 by using mb_substr instead of index access
<!--
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   (lowest branches are regularly merged to upper ones so they get the fixes too).
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Commits
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0f86156 [Console] fixed corrupt error output for unknown multibyte short option

Author: Robin Chalas

src/Symfony/Component/Console/Input/ArgvInput.php

@@ -121,7 +121,8 @@ private function parseShortOptionSet($name)
         $len = \strlen($name);
         for ($i = 0; $i < $len; ++$i) {
             if (!$this->definition->hasShortcut($name[$i])) {
-                throw new RuntimeException(sprintf('The "-%s" option does not exist.', $name[$i]));
+                $encoding = mb_detect_encoding($name, null, true);
+                throw new RuntimeException(sprintf('The "-%s" option does not exist.', false === $encoding ? $name[$i] : mb_substr($name, $i, 1, $encoding)));
             }
 
             $option = $this->definition->getOptionForShortcut($name[$i]);

src/Symfony/Component/Console/Tests/Input/ArgvInputTest.php

@@ -228,6 +228,11 @@ public function provideInvalidInput()
                 new InputDefinition(array(new InputArgument('number'))),
                 'The "-1" option does not exist.',
             ),
+            array(
+                array('cli.php', '-fЩ'),
+                new InputDefinition(array(new InputOption('foo', 'f', InputOption::VALUE_NONE))),
+                'The "-Щ" option does not exist.',
+            ),
         );
     }