Is your feature request related to a problem? Please describe.
Cosign allows publishing attestations and provenance to a repository other than the image repository using the environment variable COSIGN_REPOSITORY.

• This will be helpful in scenarios where a single digest/container image is tagged with multiple repositories and would help publish provenance to an external repository to avoid pollution in all image repositories for the same digest.
• Reduces migration effort of tags when moving signatures / provenance attestations for multiple images with same digest
• Helps to provide a single point of repository to external customers during verification of multiple images of same digest

Describe the solution you'd like
COSIGN_REPOSITORY must be allowed as an input and set as env variable for cosign command
When set, use this repository to publish provenance instead of image repository.
When unset/empty, publish provenances as per the parsed image repository (default cosign behavior)

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.