feat(cli, router, metro, asset): add basePath support (#23911)

# Why

- Add the ability to export websites for hosting from a custom path.
This is required for GitHub pages.
- Resolve ENG-9193

feat(cli, router, metro, asset): add basePath support (#23911)

# Why

- Add the ability to export websites for hosting from a custom path.
This is required for GitHub pages.
- Resolve ENG-9193
- Resolve https://github.com/expo/expo/issues/20562
- Resolve https://github.com/expo/router/issues/165

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# How

- Add `expo.experiments.basePath` which can be used during `npx expo
export` to modify how assets are referenced.
- Set the `publicPath` in Metro to output as expected.
- Add custom asset writing for web to support stripping the unused
prefix.

- It's unclear if this should also apply to native, and if we should
have platform-specific variations.
- Update Expo Router to support automatically adjusting paths to support
basePath in production builds.
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How did you build this feature or fix this bug and why?
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# Test Plan

- [ ] New `expo export` test.

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# Checklist

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- [ ] Documentation is up to date to reflect these changes (eg:
https://docs.expo.dev and README.md).
- [ ] Conforms with the [Documentation Writing Style
Guide](https://github.com/expo/expo/blob/main/guides/Expo%20Documentation%20Writing%20Style%20Guide.md)
- [ ] This diff will work correctly for `npx expo prebuild` & EAS Build
(eg: updated a module plugin).

---------

Co-authored-by: Expo Bot <[email protected]>
Co-authored-by: Aman Mittal <[email protected]>

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