Fix error in PhabricatorSetupIssueView

Summary:
- Move `prettyPrintJSON()` and make it static.
- Use it from `PhabricatorSetupIssueView`
- Update other `config/` places that use it to call it from the new class.

This fixes a bug in `PhabricatorSetupIssueView` which showed up if the value
was an array and couldn't be rendered by `phutil_escape_html()`.

Test Plan:
- Rendered some config options.
- Went to /config/issue/config.unknown.phame.skins/ without error.

Reviewers: epriestley, btrahan, chad

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2255

Differential Revision: https://secure.phabricator.com/D4411

src/applications/config/controller/PhabricatorConfigEditController.php

@@ -330,7 +330,7 @@ final class PhabricatorConfigEditController
       case 'list<string>':
         return implode("\n", nonempty($value, array()));
       default:
-        return $this->prettyPrintJSON($value);
+        return PhabricatorConfigJSON::prettyPrintJSON($value);
     }
   }
 
@@ -462,7 +462,8 @@ final class PhabricatorConfigEditController
       if (!array_key_exists($option->getKey(), $value)) {
         $value = '<em>'.pht('(empty)').'</em>';
       } else {
-        $value = $this->prettyPrintJSON($value[$option->getKey()]);
+        $value = PhabricatorConfigJSON::prettyPrintJSON(
+          $value[$option->getKey()]);
       }
 
       $table[] = '<tr>';