Support both single/multi arch image repo and add new case

• Support both single arch and multi arch image repo
  Previously, eLxr Docker images only came from Docker Hub and were multi-arch.
  However, now the Docker image may come from https://gitlab.com/elxr/tools/elxr-container/container_registry/9189615
  It's single-arch container image.
  Therefore, parameters ENABLE_AMD64 and ENABLE_ARM64 were added so that the pipeline can test both multi-arch images and single-arch images.

• Add new test case to verify sources list integrity

Signed-off-by: Chi Xu chi.xu@windriver.com