Restructure server timings so the timing name does not get lost

lib/core/engine/collector.js

@@ -219,6 +219,11 @@
             }, {});
           } else if (equals(keyPath.slice(-1), ['resourceTimings'])) {
             return {};
+          } else if (equals(keyPath.slice(-2), ['timings', 'serverTimings'])) {
+              return value.reduce((result, timing) => {
+                  result[timing.name] = timing.duration;
+                  return result;
+              }, {});
           }
           return value;
         });