Avoid continuously rebuilding the Conan build container

[jfpanisset]

The build container for Conan packages ci-baseos-gl-conan is not being correctly pushed up to Docker Hub and gets rebuilt for every
Conan package build, which is slow and wasteful.

Also separate releases get tagged with the ci-common and vfx20xx versions.

A single container image should be built as part of the ci-common build and used for all Conan packages.

[jfpanisset]

The ci-baseos-gl-conan container is being pushed to Docker Hub, aswfdocker may need to use docker buildx --pull to make sure to pull the built container from Docker Hub instead of always rebuilding it.

This Action may be useful to make sure the image on Docker Hub is up to date:

https://github.com/lucacome/docker-image-update-checker