Remove legacy auth usage of $_SESSION (#10491)

* Remove auth use of $_SESSION

Will break plugins that depend on $_SESSION, Weathermap was already fixed.
Port them to use Auth::check()/Auth::user()/Auth:id()

* revert accidental replacement

includes/html/forms/mempool-update.inc.php

@@ -12,11 +12,9 @@
  * the source code distribution for details.
  */
 
-use LibreNMS\Authentication\LegacyAuth;
-
 header('Content-type: application/json');
 
-if (!LegacyAuth::user()->hasGlobalAdmin()) {
+if (!Auth::user()->hasGlobalAdmin()) {
     $response = array(
         'status'  => 'error',
         'message' => 'Need to be admin',