Add debian packaging helpers

## Context - Currently, there's no way to quickly generate a debian package for all packages in one-go for quick development. - This PR adds a script that builds all the packages given that the dependencies are already there and installed in the system. - Note that this does NOT add the project chain of dependencies and will never be a replacement for a proper debian package build that iterates through each of the packages and builds all of them as individual packages. - However, this makes it much much easier on development machines or for people who wish to build from git and already have all the dependencies quickly build a single package that includes all and quickly deploy it without having to use systemd sysext (which requires parts of the fs tree to be immutable) or having to do a manual install. ## Example usage ``` ./scripts/pkg-deb-gitdev.sh dpkg -i ./_build/<pkg>.deb ``` That's it. Just simply running the script will automatically run `just build` and build a single debian package in the `_build` dir that's ready to be installed with dpkg.