Rewrite deserialization logic to use declarative serde struct style

[cpubot]

This PR removes the imperative deserialization logic in favor of the declarative and strongly typed struct style enabled by serde.

You'll note the

#![allow(dead_code)]

Attribute in the deserialization module. We can remove the unused fields once the trie generation is implemented; disabling the warnings for now.

[BGluth]

Yeah looks good! I don't have much to suggest for changes after going through this a handful of times. The way you're doing the JSON parsing is a huge improvement over the way I was initially attempting to implement it.

We absolutely do not need this since the whole process of cloning and fs operations are more than fast enough, but we might be able to make another major improvement on parsing speed by reading in all of the files asynchronously. Might be kind of cool but definitely not needed. 👍