Debug Docker build image

[fkorotkov]

Let's create a special *-debug tag for the agent with the agent executable and https://github.com/go-delve/delve so we can use this image in CLI to run the agent in debug mode and connect from IntelliJ to it https://www.jetbrains.com/help/go/attach-to-running-go-processes-with-debugger.html#attach-to-a-process-on-a-remote-machine.