Fix enotice when Log service is swapped out

This function is calling a property on the psr_log service that may not exist. If the
service is swapped out there is no reason the replacement should have this property.

Given it's just an array I think duplicating it is the most readable

Civi/API/LogObserver.php

@@ -23,7 +23,7 @@ class LogObserver extends \Log_observer {
    * @param array $event
    */
   public function notify($event) {
-    $levels = \Civi::log()->map;
+    $levels = $this->getLevels();
     $event['level'] = array_search($event['priority'], $levels);
     // Extract [civi.tag] from message string
     // As noted in \CRM_Core_Error_Log::log() the $context array gets prematurely converted to string with print_r() so we have to un-flatten it here
@@ -41,4 +41,28 @@ public function getMessages() {
     return self::$messages;
   }
 
+  /**
+   * Get the debugging levels.
+   *
+   * These are also on the CRM_Error_Log class but are not
+   * part of the interface that class implements so
+   * calling it from outside that class is unsafe.
+   *
+   * Yes, it's duplicated - but it's just an array!
+   *
+   * @return array
+   */
+  public function getLevels(): array {
+    return [
+      \Psr\Log\LogLevel::DEBUG => PEAR_LOG_DEBUG,
+      \Psr\Log\LogLevel::INFO => PEAR_LOG_INFO,
+      \Psr\Log\LogLevel::NOTICE => PEAR_LOG_NOTICE,
+      \Psr\Log\LogLevel::WARNING => PEAR_LOG_WARNING,
+      \Psr\Log\LogLevel::ERROR => PEAR_LOG_ERR,
+      \Psr\Log\LogLevel::CRITICAL => PEAR_LOG_CRIT,
+      \Psr\Log\LogLevel::ALERT => PEAR_LOG_ALERT,
+      \Psr\Log\LogLevel::EMERGENCY => PEAR_LOG_EMERG,
+    ];
+  }
+
 }