Change deployment base container from alpine to slim-buster

Alpine is not manylinux compatible as is. It can be tricked into advertising as such, but this comes with several problems attached. For once it is using muslc instead of glibc. Even though Python packages do install as binary manylinux wheels it is not guaranteed that that they will properly execute as glic dependencies could be unsatisfied.

Using slim-buster Python images renders container images that are similar in size compared to the alpine ones and incurs the benefits of having a standard glibc with it.