text: Title: ENH: support multiple geometry columns in read_postgis
  Body: #### Is your feature request related to a problem?
  
  I'm loading the results of a PostGIS query with multiple geometry columns, and I wish geopandas would convert all of them. The problem is that now, only one of the columns is converted to a real geometry type and the other geometries I have to convert myself using `shapely.wkb`. 
  
  #### Describe the solution you'd like
  
  `geopandas.read_postgis` should have an argument named `geom_cols: list[str]`. When this argument is set, all these columns are parsed into a geometry type. 
  
  #### API breaking implications
  
  This will add an additional optional parameter. Behaviour wouldn't change if the parameter is not included, so it would be backwards compatible if I'm not mistaken. 
  
  #### Describe alternatives you've considered
  
  Current solution is to use `shapely` to do the conversion after loading the data. 