add v prefix

[ludfjig]

What does this change

porter explain -r getporter/hello-llama:0.1.1 now prepends a v to the version (0.1.1), so that it will find the bundle if it is tagged v1.2.3 in the registry.

What issue does it fix

Closes #2886

Notes for the reviewer

Put any questions or notes for the reviewer here.

Checklist

• Did you write tests?
• Did you write documentation?
• Did you change porter.yaml or a storage document record? Update the corresponding schema file.
• If this is your first pull request, please add your name to the bottom of our Contributors list. Thank you for making Porter better! 🙇‍♀️

Reviewer Checklist

• Comment with /azp run test-porter-release if a magefile or build script was modified
• Comment with /azp run porter-integration if it's a non-trivial PR

[schristoff]

Amazing work! Are you able to add some test cases for this?

[ludfjig]

/azp run porter-integration

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