text: Title: fig.render() is used several time in a row for st_folium
  Body: I did not succeed in testing locally on my side (not sure how to deal with the _component_func), but I figured that with v0.14 version of st_folium, the main computation time is used with my use case by the "fig.render()" folium function. 
  
  This is used **twice** in the process of the map creation : 
  - first line in _get_map_string
  - first line in  _get_siblings
  
  Given these two functions are used only once in the __init__, would it be possible to mutualize the render only once on folium_map, before calling these to function ? This could improve performance drastically (once again !)