Automate SBOM generation for all CI images

[jayavenkatesh19]

Towards https://github.com/rapidsai/build-infra/issues/280

Current Approach

PR builds

• Image built and published on rapidsai/staging on Dockerhub
• Image tag is prepended with PR number gathered from GITHUB_REF
  Branch push
• Image built and published to rapidsai/<image_repo> on Dockerhub
• Image tag gathered from compute matrix is used.

Proposed changes using the multi-stage build approach

• Add a new stage in each Dockerfile called syft-base with the Syft binary installed on a minimal alpine 3.20 image.
• The main docker build is done using a stage called <ci-img>-base to differentiate it from the final image.
• Another stage is added called <ci-img>-sbom where the built stage is mounted to a specified location on the syft-base stage
• A syft-scan is done on the mounted location, and an SBOM is generated.
• The generated SBOM is then copied to the final stage, with image name and tags kept unchanged to ensure no changes to how these images are built and published.