Emit cache setup issues from cache specs

Summary:
Ref T5501. Currently, we emit some bad warnings about, e.g., "apc.stat" on PHP 5.5+ systems with OPcache, where the warnings are not relevant.

Generate and raise warnings out of the CacheSpec pipeline so we only run relevant code.

Test Plan: Faked various warnings and saw them render correctly.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5501

Differential Revision: https://secure.phabricator.com/D12318

src/applications/config/controller/PhabricatorConfigCacheController.php

@@ -40,7 +40,6 @@ final class PhabricatorConfigCacheController
     $this->renderCommonProperties($properties, $cache);
 
     return id(new PHUIObjectBoxView())
-      ->setFormErrors($this->renderIssues($cache->getIssues()))
       ->setHeaderText(pht('Opcode Cache'))
       ->addPropertyList($properties);
   }
@@ -146,20 +145,6 @@ final class PhabricatorConfigCacheController
 
   }
 
-  private function renderIssues(array $issues) {
-    $result = array();
-    foreach ($issues as $issue) {
-      $title = $issue['title'];
-      $body = $issue['body'];
-      $result[] = array(
-        phutil_tag('strong', array(), $title.':'),
-        ' ',
-        $body,
-      );
-    }
-    return $result;
-  }
-
   private function renderYes($info) {
     return array(
       id(new PHUIIconView())->setIconFont('fa-check', 'green'),