Refactor internals to work with async-interop loop spec

[staabm]

Factor out our internal stream_select based event-loop according to the async-interop spec[1] to make the stomp client play well with compatible concurrency frameworks (e.g. amphp, reactphp,..).

We need to figure out which default loop we use, in case our stomp lib is used standalone. We can either default to the impl we already have, or e.g. Use the amphp based event loop (which is per default also based on stream_select - when not high perf ev/uv php-extensions are available)

[1] https://github.com/async-interop/event-loop

[jmglsn]

I like the idea to update our lib to rely on https://github.com/async-interop/event-loop. I was attending a talk from @clue this year in Hamburg and I really would like to see our lib working on reactphp.

[jmglsn]

Let's create another repository and start a version that is designed for react-php.
We could start with some requirements, what do you think?

[staabm]

Yeah lets prototype it in a separate repos at first.

I would go with amp instead of react though.