Convert states and offshore areas to collections

[shawnbot]

Currently, the states, offshore regions, and offshore areas are listed only in CSV files. Soon we're going to need to accommodate state-specific content (and probably data), e.g. for opt-in states, which is not easy to incorporate into the CSV files. We should ditch those altogether and turn the lists of different region types into collections, which also allows us to ditch the kinda janky Jekyll plugin that currently generates the state pages and might be contributing to our slow build times.

[shawnbot]

DONE!