[Feature]: Support (re)loading from alternate path at runtime

### Description

Change path directory during runtime to support Angular localization

### Platforms

- [x] iOS
- [x] Android
- [x] Web

### Request or proposed solution

`appStartPath` was [added](https://github.com/ionic-team/capacitor/pull/8019), but since it isn't a dynamic runtime feature, it doesn't help with #3912. Feel free to reopen #3912 instead.

> ***At runtime***, we should support the use case of loading a file other than /index.html. For example: __app.html or en-US/index.html. This could also be a configuration option, but we should be able to override it at runtime to allow for use cases such as this: https://github.com/ionic-team/capacitor/discussions/3905
>
> see https://github.com/ionic-team/capacitor/pull/3405
> depends on https://github.com/ionic-team/capacitor/issues/3913

### Alternatives

_No response_

### Additional Information

_No response_