Add the following functionality to the build image script:
1. Let the user choose the container runtime of their choice. In some
systems, both Docker and Podman may be available, so we need to let
the user choose which runtime they want.
2. Let users choose if they want to save the image. For non-production
builds, we may want to simply build the container image, without
the time penalty of compression.
Ensure that when the container image is installing pymupdf (unavailable
in the repos) with verified hashes. To do so, it has the pymupdf
dependency declared in a "container" group in `pyproject.toml`, which
then gets exported into a requirements.txt, which is then used for
hash-verification when building the container.
Because this required modifying the container image build scripts, they
were all merged to avoid duplicate code. This was an overdue change
anyways.
