Allow images to be loaded from an external public source during PR/MR decoration

Users report that their SonarQube instances are not accessible publicly on the internet, while using gitlab.com Merge Request decoration or while using github.com Pull Request decoration. When GitLab/GitHub tries to load the images (for bugs, code smell, coverage etc), SonarQube instance is not reachable and the image links are broken.

On the other hand, users can have their GitLab/GitHub instances on-prem private, cut from the public internet (air-gap style or strong network isolation). For this use case, we still want to load the images from SonarQube.

We should detect if we are decorating MR/PR on cloud ALM or on-premise ALM. If it's a cloud ALM, the links in the MR/PR should point to publicly available location.