[Frontend] Fixed magnify glass in search input

open #199
open #278
Fixed z-indexing problem in :before elements
in search input (magnify glass, etc.);

platform/commonUI/general/res/sass/forms/_filter.scss

@@ -111,6 +111,7 @@
         position: absolute;
         top: 50%;
         @include transform(translateY(-50%));
+        z-index: 1;
     }
 
     &:before {