examples dir refactor + cleanup

[wkozyra95]

The examples directory is intended for internal examples, because we do not expect most users to interact with server from rust.

• Move examples from top-level create to integration_testing crate
• Refactor the code, so you can
  • Run any example in docker (instead of one specific docker example)
  • Fix issue with downloading sample assets(currently paths resolve based on the cwd)
  • Add better abstraction to simplify adding new examples with less boilerplate
• Some examples fail randomly because web socket connection is established too early (probably some sleep would fix the issue)