Added new field in the BldConfig for docker registries that supports url, username and password.
Added new optional configuration in the runs_on section of a pipeline in order to define a registry configuration with url, username and password or use a key to lookup a registry from the bld configuration.
Added support for expressions in all variants of a registry section in a pipeline.
Made changes to the platform in order to pull an image from a registry based on the provided configuration.
In this PR: