Add namespaces to exec window (#15454)

.changelog/15454.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+ui: Fixed a bug where the exec window would not maintain namespace upon refresh
+```

ui/app/controllers/exec.js

@@ -17,7 +17,7 @@ export default class ExecController extends Controller {
   @service system;
   @service token;
 
-  queryParams = ['allocation'];
+  queryParams = ['allocation', 'namespace'];
 
   @localStorageProperty('nomadExecCommand', '/bin/bash') command;
   socketOpen = false;