Ensure a fresh base image for docker builds #1045
Description
We are currently building from node slim series of debian docker images.
These images are known to have problems with being potentially old at build time and simply way too large for their purpose and causing us slow builds.
The slow builds can be excused if they where fresh but they are having freshness issues.
We currently cant target alpine based images due to upstream bugs.
The currently proposed idea for solving this would be via moving to a Nix based build process as some other matrix ecosystem projects already use.
After Draupnir 3.0 this is a realisticly viable path as the complexity of building on Nix will have taken a massive nosedive due to the move away from Yarn to npm that is part of 3.0