fix(reactivity): add existing index or non-integer prop on Array should not trigger length dependency

[xxgjzftd]

Fixed the scenarios below:

const observed = reactive(new Array(3))
effect(() => {
  console.log(observed.length)
})
observed.x = 'x'
observed[-1] = 'x'
observed[1] = 1
// all they three statement will trigger the effect which would not be the expected result...