chore: reduce unused web code

[EvanBacon]

Why

Web bundles are too big by default, this is one of a series of PRs that will reduce code that is pulled in on web.

How

Because we compile the src of @expo/metro-runtime to CJS, the react-native-web shaking plugin breaks and we import everything. This PR also switches the input for @expo/metro-runtime to be src for both web and native, while using build for Node.js and types.

Test Plan

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).

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⚠️ Suggestion: Missing changelog entries

Your changes should be noted in the changelog. Read Updating Changelogs guide and consider adding an appropriate entry to the following changelogs:

• packages/@expo/metro-config/CHANGELOG.md
• packages/expo-router/CHANGELOG.md

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