This patch bakes browsers into docker image.
Important observations:
- We now re-build docker image everytime we roll browsers.
- Docker image size almost doubles: from `225MB` to `496MB`.
References #2926
- Repository name has to start with `public/` to be exported to dockerhub.
- Remove `DOCKER_USERNAME` to avoid unnecessary masking in our logs.
- Publish dev versions of Docker image only when changes to docker file
happen. (this is why NPM publishing and Docker publishing for dev
releases are now separate).
- Release publishing in two separate jobs to make them independent.
References #2926