This PR adds a new FB-specific configuration of Flight. We also need to
bundle a version of ReactSharedSubset that will be used for running
Flight on the server.
This initial implementation does not support server actions yet.
The FB-Flight still uses the text protocol on the server (the flag
`enableBinaryFlight` is set to false). It looks like we need some
changes in Hermes to properly support this binary format.
Code organization PR.
It looks like the `ReactServerStreamConfigFB` is only used in the
`relay-server` package. This PR moves it to `react-server` from
`react-server-dom-fb` (similar to how we have config for bun, for
example). This avoids cross-package imports from `react-server` to
`react-server-dom-fb.`
Andrey Lunyov