Test Docker images in CI

[ZanSara]

Problem
Right now, Docker images are not tested in CI. We test them manually before release, but this process is tedious and error-prone (see for example #3692)

Proposed solution
We should add a CI workflow that tests that the images are functional. For example we could start from a workflow that starts the REST API images and test the REST API respond on the /initialized endpoint.

[masci]

Let's start with two basic tests:

• Assert Haystack version docker run --rm deepset/haystack:base-gpu-v1.12.2 python -c"import haystack; print(haystack.__version__)" is 1.12.2
• docker-compose up the default docker_compose.yml file and assert curl http://localhost:8000/hs_version returns the expeted version (something equivalent with a simpler setup would be better)

[silvanocerza]

Fixed by #3943, #3976, #3982 and #4004.