This adds support for listing all of the supported distributions,
their arches, the image types, and their repository details.
This returns 3 nested json objects. The keys for the first layer are the
distribution names. The 2nd layer's keys are the architectures supported
by that distribution, and the 3rd layer's keys are the image types
supported by that distribution:architecture pair. The value of the 3rd
layer is the repository information.
Resolves: RHEL-60133
44ac65b70c