feat(scheduler): prevent from maximum recursive updates

[theniceangel]

The demo is as follows:

  const state = reactive({ count: 0 })
  let dummy
  watch(() => {
    dummy = state.count
    state.count++
  })

flushPostFlushCbs dost not check maximum recursive updates, the code above will cause a maximum call exceed

[yyx990803]

Good catch. I just realized we are missing tests for the scheduler due to a big refactor. Would you be interested in adding some? (can be based on these old tests)

[vue-bot]

Hey @theniceangel, thank you for your time and effort spent on this PR, contributions like yours help make Vue better for everyone. Cheers! 💚

[theniceangel]

@yyx990803 no problem.