[Flight][Java] Add optional session headers

- Add a client middleware which receives and re-uses a session token from the server.
- Add a server middleware which, when encountering a request with no session header, creates a session on the backend, generates a token for it, and sends the token to the client in a header. The client can re-use this as indicated above.
- If the client has a session header, re-use the same session from the backend (report an error if an invalid session was used).

**Reporter**: [Tiffany Lam](https://issues.apache.org/jira/browse/ARROW-10427) / @tifflhl

_{**Note**: *This issue was originally created as [ARROW-10427](https://issues.apache.org/jira/browse/ARROW-10427). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}

Start by locating the Java client and server middleware entry points responsible for request and response headers, then trace how backend sessions and invalid-session errors are represented. Define the client and server integration tests needed to cover token creation, reuse, and invalid tokens; done means both middleware paths consistently share the backend session.

Written by the indexing model from the issue text.