Improve container support in tox.ini

Improve container support in tox.ini

- modify tox.ini to use dedicated scripts that can detect a local podman
  installation and use it instead of docker.
- replace nbiotifications docker-compose YAML file by a standalone
  container directly runnable with docker or podman.

Podman.io is a rootless and serverless alternative to Docker.io.
It avoids using sudo in many cases, what is a good thing.
It is now prefered to Docker.io by many linux distributions.

https://podman.io/
https://access.redhat.com/solutions/3696691
https://thesynack.com/posts/docker-compose-podman/
https://martinheinz.dev/blog/35

Signed-off-by: guillaume.lambert <guillaume.lambert@orange.com>
Change-Id: I593568b2e17bebe784eff7b3413d0d5b829f2ade