better support for lines on maps in Plotly Express

Today, px.line_mapbox and px.line_geo expect rows which are points, which are then split into groups and connected by lines.

In most GIS formats, however, as wrapped by GeoPandas, the entire line feature is often stored in a single row, just like choropleth geometries. We should have either a new pair of PX functions for this (px.line_feature_mapbox?) or an option to the existing functions (px.line_mapbox(geojson=<geojson>)) to support this option out of the box.

首先检查现有的 px.line_mapbox 和 px.line_geo 入口点，以及它们如何将行解释为点。将该行为与 GeoPandas 和 GIS 格式中的单行线要素进行比较。完成的要求是确定一项双方认可的设计——新增 PX 函数或为现有函数增加一个选项——并默认支持这些线要素。