Merge #2958

2958: Optional local address r=coot a=Infinisil

This changes the type of `daLocalAddress` from `Either Socket FilePath` to `Maybe (Either Socket FilePath)`, allowing having no local address at all, which is useful if there's no need for node-to-client communication.

I also made a refactoring of the `withAsync` calls to remove the nesting, using [`Async.Concurrently`](https://hackage.haskell.org/package/async-2.2.3/docs/Control-Concurrent-Async.html#t:Concurrently)'s `Alternative` instance, which runs threads concurrently, waiting for the first result.

Co-authored-by: Silvan Mosberger <[email protected]>

Author: iohk-bors[bot]