hack: add build-image for abstracting the hard parts of image building

Add a python-based script `build-image` that takes on the complexities
of how we build our images, including applying common tags and
"fully-qualified image names". The script can be called from a makefile
but doesn't require it. When used directly you can generate
multiple image variants in one pass.
Example:
```
./hack/build-image -k server -p default -p nightly -a amd64 -a arm64
```
Will produce four images, in short:
1. server with default packages on amd64
2. server with default packages on arm64
3. server with nightly packages on amd64
4. server with nightly packages on arm64
(all using the default distro, currently fedora)

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn