Fixes docker image cross-build (part 2)

[merschformann]

Description

This PR means to fix the arm64 docker image (cross-built on amd64) by using a self-contained single binary build (previously dotnet included amd64 .so files on an arm64 build for non-intuitive reasons). This should finally make the new linux/arm64 work properly.

Changes

• Restructures SC.Service Dockerfile build to create a single binary build to wrap up in the docker image
  • Side-effect: reduces the docker image size from previously 327MB to 121MB
• Reverts the default internal port to 80 for better backwards compatibility
• Minor release script improvements