change: if default storage class exists use 10Gi PVC for registry (#1974)

[iwilltry42]

Ref #1974

So far, the registry was backed by an EmptyDir, so restarts/redeployments, e.g. as part of an upgrade cleared the registry and we would end up with image resources backed by nothing in the registry.
With this PR we get a basic 10Gi PVC backing the registry if there's a default storage class defined upon installation.
As discussed, there are not configuration options available.

Checklist

• The title of this PR would make a good line in Acorn's Release Note's Changelog
• The title of this PR ends with a link to the main issue being address in parentheses, like: This is a title (#1216). Here's an example
• All relevant issues are referenced in the PR description. NOTE: don't use GitHub keywords that auto-close issues
• Commits follow contributing guidance
• Automated tests added to cover the changes. If tests couldn't be added, an explanation is provided in the Verification and Testing section
• Changes to user-facing functionality, API, CLI, and upgrade impacts are clearly called out in PR description
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