add rancher upload artifacts cmd

[tashima42]

Add a command to download GitHub artifacts and upload them to the prime-artifacts bucket, replacing the registry info

release upload rancher artifacts v2.8.3

config:

     "v2.8.3": {
       "release_branch": "release/v2.8",
       "dry_run": false,
       "skip_status_check": true,
       "rancher_repo_owner": "rancher",
       "base_registry": "docker.io",
       "registry": "registry.rancher.com",
       "prime_artifacts_bucket": "prime-artifacts"
     },

[briandowns]

Can you add this new config section to the test config in test data ?

[tashima42]

Updated