Modify composer to use RepoRegistry, instead of loading the host
repositories, when initializing WeldrAPI.
Modify WeldrAPI to use RepoRegistry, instead of a map of repository
definitions. Make sure that the RepoRegistry method specific to image
type is used in Welder where appropriate. Specifically when depsolving a
Blueprint, which is used to build a specific image type. Update Weldr
API unit tests to reflect the change.
Add a new method to RepoRegistry, allowing to get list of repositories,
which should be used for building an image for a given architecture,
without specifying the exact image type. Add relevant unit tests.
Signed-off-by: Tomas Hozza <thozza@redhat.com>