feat(cli): support customizing the Metro resolver

[EvanBacon]

Why

This PR adds the ability for users to chain the Metro resolver in their metro.config.js in order to customize file resolution.

How

• Refactor custom resolving to support a user-defined resolver that runs before Expo CLI's resolver.
• Mutate the context ahead of time to ensure users have access to the multi-platform settings that we'll resolve against.
• Update the docs with a bunch of tips and tricks I wish I knew years ago.
• Move the expo-router AppContainer shim to expo/cli.
• Restructure resolution cases to prevent plugin-based conventions from leaking into each other. For example, Node.js external shims are no longer tested against tsconfig path aliases.

Test Plan

• Updated unit tests to cover existing behavior better.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.dev and README.md).
• Conforms with the Documentation Writing Style Guide
• This diff will work correctly for npx expo prebuild & EAS Build (eg: updated a module plugin).