release-upload: generate checksums of artifacts

[smelc]

Context

• This is the cardano-node version of release-upload: create file with checksums of binaries cardano-cli#762
• Was asked by a user: [FR] - Release artifacts checksums - where??? cardano-cli#755 (comment)
• Anyway a good practice to make it possible for users to verify the integrity of their downloads and a number of deployments tools require assets to have attached checksums.
• The change of version of {download,upload}-artifact is motivated by the fact that v3 will be shutdown at the end of the year: https://github.com/actions/upload-artifact#actionsupload-artifact

How to trust this PR

• Look at the assets generated when producing a release with this PR: https://github.com/IntersectMBO/cardano-node/releases/tag/untagged-0ccd023f738aead32ba8
• Observe it contains the checksums:

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• Self-reviewed the diff

[carbolymer]

makes senses 👍🏻