Move rest module into a separate package with minimal dependencies

[ZdenekM]

We would like to use arcor2.rest in different projects. It is quite versatile and handy and, in contrast to everything else that exists (up to my knowledge), supports typing and dataclasses, which makes development less error-prone. Unfortunately, there is a lot of stuff in arcor2, which leads to many dependencies, so it makes sense to make arcor2.rest into arcor2_rest - to make it usable in different projects without the need to install a lot of stuff. I haven't done an analysis yet, but it will probably be necessary to create also arcor2_exceptions, etc., to allow this.