Simplify caching of status checks and fixes missing domain_id condition

Fixes a few apparent problems:
- domain_id was ommitted causing unexpected results
- Civi::cache was being read but never written to
- Object caching did not persist in memory across different check classes
- If we did write to Civi::cache there is no mechanism for clearing that cache when data changes

Solution: use simple array cache in Civi::$statics

CRM/Utils/Check/Component.php

@@ -18,11 +18,6 @@
  */
 abstract class CRM_Utils_Check_Component {
 
-  /**
-   * @var array
-   */
-  public $checksConfig = [];
-
   /**
    * Get the configured status checks.
    *
@@ -32,20 +27,12 @@ abstract class CRM_Utils_Check_Component {
    * @throws \Civi\API\Exception\UnauthorizedException
    */
   public function getChecksConfig() {
-    if (empty($this->checksConfig)) {
-      $this->checksConfig = Civi::cache('checks')->get('checksConfig', []);
-      if (empty($this->checksConfig)) {
-        $this->checksConfig = StatusPreference::get(FALSE)->execute()->indexBy('name');
-      }
+    if (empty(Civi::$statics[__FUNCTION__])) {
+      Civi::$statics[__FUNCTION__] = (array) StatusPreference::get(FALSE)
+        ->addWhere('domain_id', '=', 'current_domain')
+        ->execute()->indexBy('name');
     }
-    return $this->checksConfig;
-  }
-
-  /**
-   * @param array $checksConfig
-   */
-  public function setChecksConfig(array $checksConfig) {
-    $this->checksConfig = $checksConfig;
+    return Civi::$statics[__FUNCTION__];
   }
 
   /**