First step to GA'ing the currently v1alpha1 APIs. Don't add to payload
manifests yet, and the featuregate is retained.

Mostly fixups, with some minor changes to the v1alpha1 API:

 - Removed Version and ConfigGeneration from MOSB as they were unused
 - Updated relatedobjects list
 - Changed all optional,omitempty structs to pointers
 - Removed default for ImageBuilderType, but keeping default build arch
   to noarch as we don’t foresee changing that.
 - Fixed RenderedImagePushspec validators to match description

 - Update from PodImageBuilder to JobImageBuilder, and add a
   MachineOSBuild reference to MachineOSConfig
 - Failed and Interrupted will now cause MOSBuild conditions to be
   immutable
 - Updated Arch enum to be PascalCase
 - Updated relatedObject go doc based on suggestion
 - Add validation for buildEnd > buildStart
 - Removed conditions field from MOSConfig. The build object is
   supposed to reflect conditions instead, so this is not needed
   at this time
 - Use dns1123 format check for all strings that match, and otherwise
   switch pattern checks to validation rules where appropriate
 - Updated godocs a bit more for formatting

Mostly fixes around validation and godocs. Added some additional test
cases.

 - Removed BuildOutputs and the CurrentImagePullSecret field
   (not really needed at this time, we’d prefer if the user
   would put any additional pull secrets into the cluster-wide
   object)
 - Removed BuildInputs and lifted all fields to spec, removing:
    - ReleaseVersion
    - BaseOSImagePullSpec
    - BaseOSExtensionsImagePullSpec
   Which will be populated directly from the MCO instead. We will
   consider re-adding those if there is a need for on cluster
   pre-builds off new release images in the future.
 - Renamed finalImagePushSpec to digestedImagePushSpec
 - Switched MachineOSBuilderReference back to an union, and renamed
   the job object unionmember to just “job”
 - Changed “desiredConfig” to “MachineConfig” for clarity
 - Kept ObservedGeneration, but updated the validation, and will
   fix on the MCO side
 - Removed duplicate arch types, and updated containerfiles to allow at
   most 1 per arch (minus noarch)

These were added for the alpha API originally, but they seem to have
been removed during a refactor of the tests. The current tests are a
duplicate of bootimage tests.