Bring ReactFabricHostComponent back to react-native (#36570)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/36570

I'm doing some preparations to implement this proposal to bring some DOM APIs to React Native refs: https://github.com/react-native-community/discussions-and-proposals/pull/607

To make it easier to iterate on the proposal, and to improve the separation of concerns between React and React Native, I'm moving the definition of `ReactFabricHostComponent` (the public instance provided by React when using refs on host conmponents) to the `react-native` package.

I already did some steps in the React repository to simplify this:
* Removing unused imperative events that caused increased coupling: https://github.com/facebook/react/pull/26282
* Extracting the definition of the public instance to a separate module: https://github.com/facebook/react/pull/26291

In this case, in order to be able to move the definition from React to React Native, we need to:
1. Create the definition in React Native and export it through `ReactNativePrivateInterface`.
2. Update React to use that definition instead of the one in its own module.

This diff implements the first step.

`ReactNativeAttributePayload` is required by this definition and by the one for Paper that still exists in React. I moved it here so we only define it where we use it when we remove Paper. Paper will access it through `ReactNativePrivateInterface` as well. That will also allow us to remove a few other fields in that interface.

Changelog: [Internal]

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Reviewed By: yungsters

Differential Revision: D43772356

fbshipit-source-id: 78dac152f415f19316ec90887127bf9861fe3110