Introduce Wally development containers

This PR introduces two development containers, tagged as builder and devel, each including all dependencies required to develop and test the Wally processor.

• builder images intended for CI workflows
• devel images intended for end-users

These containers will serve as a quick start for setting up a development environment and testing the Wally processor. The container build workflow produces images for both amd64 and arm64 platforms.

Currently marked as a draft, as the ARM build depends on an upcoming upstream release from the SAIL project. Container images without sail installed are available temporarily here for testing/demo purposes:

• https://github.com/doganulus/cvw/pkgs/container/wally

Note that the current base image is Debian 12. We can discuss this choice along with what should be included in the containers.