Parallelize the creation of plant_parts_eia

[katie-lamb]

Now that plant_parts_eia is dagsterized and part of the ETL, it's a bit of a bummer that it takes so long to generate. Currently, there's a loop in the creation of the table here that loops through all the different parts and concatenates a bunch of dataframes together. This could be done concurrently instead of looping to speed things up.