fix(runtime-core): avoid infinite loop rendering caused by setting props multiple times

[HcySunYang]

Fix: #3371

I made a minimal reproduction https://codesandbox.io/s/vigilant-euler-7q6j0?file=/src/index.ts. Open the link and check the comments in the code

1. The Parent component accesses the props of the Child component and is tracked by the Child component's props.
2. When rendering the Child component, the Child component modifies the reactivity data of the Parent component.
3. The Parent component re-rendering and checks whether the Child component needs to be updated.
4. Child component needs to be updated, and set the full props
5. For the props.foo, it needs to be cast to a boolean value
6. So the props.foo been modified twice, once is set to the empty string, and another is set to a boolean value. here and here

[edison1105]

I think this will be better

   for (const key in rawProps) {
      // key, ref are reserved and never passed down
      if (isReservedProp(key)) {
        continue
      }

      const value = rawProps[key]
	 //...
    }

[yyx990803]

This adds two additional object key enumerations each call which is not ideal - I managed to avoid them in 0255be2