Integrate and remove dependency on Airbnb ESLint rules

[aduth]

🛠 Summary of changes

Updates ESLint configuration to integrate relevant rules from the Airbnb ESLint configurations eslint-config-airbnb and eslint-config-airbnb-base.

Why?

• Incremental step toward migrating to ESLint 9 (updated configuration syntax not supported by Airbnb shared configurations)
• More explicit control over rules relevant to our projects
  • No longer need to disable stylistic rules for Prettier compatibility
  • Avoid unnecessary configuration for tools and practices not relevant to our projects (e.g. in the course of this exercise, I discovered that Airbnb includes a number of configuration for React component classes, and other tools like Vue.js)
• Shallower dependency tree, fewer dependencies to maintain
• More honesty with how we communicate our JavaScript coding standards
  • We've claimed to follow the TTS JavaScript style recommendations, but we've so far diverged from the base configuration that this is mostly untrue. Keeping the dependency has largely been due to trying to maintain this claim more-so than actually needing it.

The intent of these changes is to largely keep an identical configuration to what existed previously. Minor revisions have been incorporated based on observations of the flattened configuration, reflected in the CHANGELOG.md.

These changes were implemented using ESLint's --print-config option to display the fully-resolved configuration, rearranging the result into relevant sub-configurations (TypeScript, Mocha, Prettier, etc.).

📜 Testing Plan

Verify that build passes.

Verify that lint passes:

yarn lint

[zachmargolis]

LOL at this being the unicode infinity instead of like of the JS Infinity constant, probably better JSON compat this way?

[aduth]

Heh, hadn't noticed that 😅 I'd guess so? Though I could imagine the literal "Infinity" would work just as well too, and not require looking up the unicode character. 🙃

[zachmargolis]

should we state that our config is "inspired by Airbnb's" or have we diverged from that too much?

[aduth]

Eh, yeah, I dunno that it's particularly useful to maintain the historical alignment or imply that we still seek to keep that alignment. In the future, I think we could also do to trim down the configuration a bit more, I just didn't want to change too much too quickly in this initial pull request.