[Feature] 是否支持series标签重叠时自动重新计算标签位置，不隐藏

### What problem does this feature solve?
效果类似下图：

### What does the proposed API look like?

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Start by reproducing the overlapping series-label case shown in the attached image and locating the label-layout entry point for the affected chart series. Define the expected repositioning behavior and proposed API before implementation; done should mean overlapping labels are automatically repositioned instead of hidden, with coverage for the reproduced case.

Written by the indexing model from the issue text.