Restructure repo to report on missing dependencies

[cartogram]

Description

Fixes #1001

The changes in this PR allow us to turn on the eslint rule no-extraneous-dependencies. This is a big change so I'm breaking down the three major things happening here:

1. I moved all of the packages to packages/@shopify to allow the eslint rule to recognize the packages in this repository properly. More context in this issue Prevent missing @shopify/* packages from going out to releases #1001

2. Adjusted our .eslintrc to automatically populate the overrides for each package in this repo to only look locally in that package for existing dependencies.

3. With the above 2 changes, it now successfully reporting errors and the final changes are me retro-actively applying the missing dependencies for the ~200 times we broke this rule, but got lucky in that it didn't break anything.

Additional things

• Point 3 is work in progress, I want to get a general approval before going through that additional effort.
• In the config for the rule I chose to devDependencies: true, optionalDependencies: false, peerDependencies: true, as it seemed like the best way to accommodate the missing react/react-dom dependencies across this repo.
• This PR seems a little over-the-top, but I think organizing the repo in this way would have been good idea anyways. Mat brought up the point of migrating to a quilt framework more easily which I agree with.
• Anything repercussions of this change that I am missing? For example, additional libraries being in conflict when packages are installed in other projects?

[GoodForOneFare]

I'd prefer it if this PR was just step 1. It's unlikely that I'll accurately review this once 200+ dependency fixes are in.

[GoodForOneFare]

^ That aside, great job on figuring all of this out 👍 It's well on the way to solving a significant pain point for us and our consumers 🎉

[cartogram]

Closing this PR. @lemonmade has a different solution in the works that doesn't require the massive restructure.