[feature]: Consolidate code for registry login into script

[saisatishkarra]

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• When setting an additional provenance registry, it requires a login script that is a duplicate of signing into the image registry

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• This code needs to be consolidated into a shell script and be reusable

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Additional context
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• Duplicate code caused by: feat: Set cosign-repository input and env #2962
• Relates to: [feature]Add COSIGN_REPOSITORY input for the generator_container_slsa3 workflow #2956