enable multiple hover boxes for overlapping/multiple points

This has been tested in version 4.7.1.

When hover information is shown for points e.g. in a scatter plot, the following situations can occur:

• there are multiple points on exactly the same coordinates
• there are multiple points close to the same coordinates and the markers used to visualize those points overlap in the graph

Hover information for all those multiple points should be shown, especially in cases where the hover information includes additional data not shown directly in the graph.

The hvPlot library does this correctly: it shows stacked hover boxes for all the data points under the cursor. Plotly only shows one hover box and it is not clear which one.

I think this is an actual bug since it makes it easy to miss data and the hover information does not represent the actual data in the graph.

Here is an example using the Iris data set and Plotly:

import plotly.express as px
from bokeh.sampledata import iris
df = iris.flowers.copy()
fig = px.scatter(df, x="sepal_length", y="sepal_width", color="species",
                 opacity=0.4, hover_data=["petal_length", "petal_width"]
                )
fig.show()

This shows:

With hvPlot:

df.hvplot(kind="scatter", 
          x="sepal_length", y="sepal_width", by="species", 
          hover_cols=["petal_length", "petal_width"], 
          alpha=0.4)

首先使用提供的 iris 数据集和 px.scatter 示例复现点重叠时的行为，然后将其与 hvPlot 的结果进行比较。跟踪 fig.show() 如何为重合或重叠的点渲染 hover 信息，并确定相关的 Plotly 组件边界。完成的标准是：光标下的所有点都能获得可区分的 hover 信息，并且针对完全重叠和接近重叠两种情况都有回归测试覆盖。