perf(Mutation): drop object spread operation in patch()

patch() method on Mutation can be heavily used during large amount of
database upsert operations. Yet it is performing poorly for seemingly
simple operation (updating `this.params`). The object spread seems to
be the culprit.

In this PR, simple "loop + assignment" is used to prevent
unnecessary object creation as in the original implementation.

Note: `Object.assign` is sadly not available for targeting ES5.
Otherwise, it would be an even better choice.

Author: chuan6

src/storage/modules/Mutation.ts

@@ -99,7 +99,9 @@ export class Mutation {
   }
 
   patch(patch: Object) {
-    this.params = { ...this.params, ...patch }
+    forEach(patch, (val, key) => {
+      this.params[key] = val
+    })
     return this
   }