[Bug] Stacked Bar Animation has gaps between series

### Version

5.4.2

### Link to Minimal Reproduction

See example in docs page: https://apache.github.io/echarts-handbook/en/how-to/chart-types/bar/stacked-bar/#

### Steps to Reproduce

1. View the stacked bar in the docs
2. Reload the page so the transition animates

### Current Behavior

1. There are gaps between the series as they animate in, each of the bar series "fills" up independently, meaning the transition looks odd


### Expected Behavior

1. There are no gaps between the series as they animate in.

This could either be:

Option A. each series starts from zero thickness, at the x axis, and expands to its full extent, with the series also "moving up" as they go
Option B. the bar animates as a single unit, and the series are revealed as the animation progresses

I have tried to illustrate this below. Time is progressing left to right.

### Environment

```markdown
All, as far as I am aware!
```

### Any additional comments?

It's possible this is "expected behaviour" and therefore a feature request not a bug. But it does look very strange.