Add registry server flag on upgrade

[JoeMcGuire98]

Proposed changes

Currently the upgrade to version (image tag) is baked into the CLI, and the registry server value defaults to whatever the mesh was last deployed with. This change will allow users to override those values with flags in the upgrade command.

Checklist

Before creating a PR, run through this checklist and mark each as complete.

• [x] I have read the CONTRIBUTING doc
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] I have checked that all unit tests pass after adding my changes
• [x] I have updated necessary documentation
• [x] I have rebased my branch onto main
• [x] I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

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