[core] Use the src folder as the Metro target

[tsapeta]

Why

Following up on #29244

How

Followed #29244, but for expo and expo-modules-core packages.

• replaced build with src in the entry point
• set emitDeclarationOnly to true in TS configs
• rebuilt files – this removed .js and .js.map files from the build folder
• updated relative paths in a few places: mocks in jest-expo, @expo/metro-config and AppEntry

Test Plan

Tested in bare-expo on iOS and web and confirmed that:

• changing files in src automatically reloads the app without running yarn build
• stacktrace in the LogBox/RedBox correctly jumps to the right line in the source code

[expo-bot]

The Pull Request introduced fingerprint changes against the base commit: d8114cd

Fingerprint diff

[
  {
    "type": "dir",
    "filePath": "../../node_modules/expo",
    "reasons": [
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    ],
    "hash": "e39701ffc215df207db804dc1a44fc5c6363b6e6"
  },
  {
    "type": "dir",
    "filePath": "../../packages/expo",
    "reasons": [
      "expoAutolinkingIos",
      "expoAutolinkingAndroid",
      "expoConfigPlugins",
      "expoConfigPlugins"
    ],
    "hash": "d7e91c582bf1df8ff9e7d22cba3d0bb190a47967"
  },
  {
    "type": "dir",
    "filePath": "../../packages/expo-modules-core",
    "reasons": [
      "expoAutolinkingIos",
      "expoAutolinkingAndroid"
    ],
    "hash": "fbb4351e75bb473a2d79245b7a2a3293acc59290"
  }
]

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[expo-bot]

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⚠️ Suggestion: Missing changelog entries

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

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