Improve CI pipeline for building docker images

We should have the following stages: 

• Build
  • build qt5
  • build qt6
  • build qt6 + wasm (needs build qt6)
• Test
  • test qt5 (dependencies - build qt5)
  • test qt6 (dependencies - build qt6)
  • test qt6 + wasm (dependencies - build qt6)
• Deploy
  • docker push qt5 (dependencies - build qt5)
  • docker push qt6 (dependencies - build qt6)
  • docker push qt6+wasm (dependencies - build qt6+wasm)

This means that all the BUILD stages should have an artifact created (.tar.gz) which is passed to the relevant TEST and DEPLOY stages. In addition to this, a file should be created which contains relevant the name of the DOCKER_IMAGE, which can be used in the TEST, DEPLOY stages.

In the TEST and DEPLOY stages, we should use "docker load" to load from the tar.gz file and perform the relevant docker push. 

Why this is important? Because right now, we are building and pushing things already to DEPLOY, even when we have not tested the docker build. This will cause damage in long run.