tracking issue: beta milestone

[webern]

Tracking issue for all sub-issues that are required for somewhat of a minimum viable product of out-of-tree builds. This will require the use of external kits from the Bottlerocket project. At this stage these will not be published externally, but provided one can build the Bottlerocket kits and place them in a container registry, then Twoliter should be able to use them and build an out-of-tree variant with some custom package definitions.