Draft: ospack-base: Introduce common base ospack

In !499 (closed) I tried to create a common base ospack to reduce code duplication. This MR has been started with the goal of to reducing code duplication.

There is a lot of duplicated code between the different ospacks; and there is no real place to start if one would like to start from a base ospack (the fixedfunction ospacks contain nginx so arguably they are not minimal enough to be a base image).

So let's create a base ospack and move the common ospack bits into a seperate recipe on the path to abstracting out the common parts of the image recipes into a common base.

Leaving as a draft as currently more refactoring is required.