This allows for container locations and versions for the CAPI functions
to be (optionally) driven by the `versions-airshipctl` versions
catalogue. In addition, this moves the clusterctl config from the site
level to become its own function, which can be further refined
(e.g. for public cloud providers) via inheriting functions, composites,
types, etc.
Change-Id: Ic2b02e256419ee8536f5237327cce2754fd0abff
Closes: https://github.com/airshipit/airshipctl/issues/316
70ec47096c