Add option to upload-resource to upload an OCI image directly from a file.

[lengau]

What needs to get done

charmcraft upload-resource should be able to upload an OCI image directly from a file rather than requiring a digest and extracting it from a registry.

Why it needs to get done

It's silly to have to rockcraft pack, then upload to a registry, only for charmcraft to download from the registry when uploading to charmhub.

This will also work as a workaround for #1685

[syncronize-issues-to-jira]

Thank you for reporting us your feedback!

The internal ticket has been created: https://warthogs.atlassian.net/browse/CRAFT-2992.

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[lengau]

Duplicate of #1684