Replace all "setQueryParam()" calls with "remove/replaceQueryParam()"

Summary: Ref T13250. See D20149. Mostly: clarify semantics. Partly: remove magic "null" behavior.

Test Plan: Poked around, but mostly just inspection since these are pretty much one-for-one.

Reviewers: amckinley

Reviewed By: amckinley

Subscribers: yelirekim

Maniphest Tasks: T13250

Differential Revision: https://secure.phabricator.com/D20154

src/applications/search/controller/PhabricatorApplicationSearchController.php

@@ -905,7 +905,7 @@ final class PhabricatorApplicationSearchController
       $engine = $this->getSearchEngine();
       $nux_uri = $engine->getQueryBaseURI();
       $nux_uri = id(new PhutilURI($nux_uri))
-        ->setQueryParam('nux', true);
+        ->replaceQueryParam('nux', true);
 
       $actions[] = id(new PhabricatorActionView())
         ->setIcon('fa-user-plus')
@@ -915,7 +915,7 @@ final class PhabricatorApplicationSearchController
 
     if ($is_dev) {
       $overheated_uri = $this->getRequest()->getRequestURI()
-        ->setQueryParam('overheated', true);
+        ->replaceQueryParam('overheated', true);
 
       $actions[] = id(new PhabricatorActionView())
         ->setIcon('fa-fire')