These RequiredSizes are a map that is passed on to the partition table
logic which had hardcoded defaults. This makes it possible to define
either no RequiredSizes (`nil`) or empty RequiredSizes which means no
further constraint checks or partition resizes will be done.
This abstracts away the manifest instantiation. The idea is that we define one
of these image kind types to represent a group of image types that are
sufficiently similar. Each image kind will have a struct with with all the
properties that can be customised for the image and a function to turn that into
an actual manifest. This is similar to how distro/fedora/manifest.go and
cmd/osbuild-playground works today, and aspires to move these closer together
and to eventually make the distro definitions simpler.
For now cmd/osbuild-playground is moved over to using the new abstraction.
We have three kinds of operating system trees, until we unify them to one,
hide them behind one interface. Use this to read the architecture from the
Tree rather than pass it in as a string to parent pipelines.
Also, make the filename parameter optional in a few places, there should be no
reason to set this rather than introspect it (except for backwards
compatibility).
Lastly, add another playground example sample to build a raw image.
For now all it does is represent the name of the runner and what requirements
it has of the build pipeline.
Move some package definitions from the runner package set to where it belongs.
