adjust workflows to new branch structure

[taukakao]

The changes make it possible to build main with the Vib Workflow by automatically changing the :dev tag to :main during building.

They also add a workflow to easily sync the main branch with the dev branch on demand, while checking if core image is up to date as well.

When this is trough, I will add these changes to the other images as well.

[taukakao]

Seems that implementing this correctly is pretty much impossible due to branch protection rules.