Clean up states in EIA861 balancing authority association table #2414
Description
The state column in balancing_authority_assn_eia861 contains some invalid values and needs to be constrained / encoded appropriately. It looks like it should include US states, territories, and outlying areas abbreviations from the POLITICAL_SUBDIVISIONS table, but it also has some NA values which we've replaced with NA, and a few codes that just look bad, including CN (China? Connecticut?) and should be re-coded appropriately.