Fuchsia: Switch to gfx_tests sandbox configuration

src/tests/BUILD.gn

@@ -140,6 +140,10 @@ if (is_win || is_linux || is_mac || is_android || is_fuchsia) {
         "$angle_root/src/libANGLE/renderer/vulkan:angle_vulkan_entry_points",
       ]
     }
+
+    if (is_fuchsia) {
+      manifest = "//build/config/fuchsia/gfx_tests.cmx"
+    }
   }
 }