Add a new command to setup a cleanup policy for functions artifacts

[taeold]

Add command functions:artifacts:setpolicy.

This new command leverages Artifact Registry's cleanup policies feature. Cleanup policies are a managed service feature that automatically removes container images based on configurable rules, providing a more robust and transparent solution.

The command simplifies the process of configuring these policies for Cloud Run functions repositories. By default, the command sets up a policy that deletes images older than 3 days. Users can easily adjust this retention period using the --days option.

The command handles checking if the user already has a cleanup policy set up. The cli command will check if a clean up policy exists, and if so, will prompt the user if they wish to proceed.

[inlined]

LGTM. I assume this can go in as reverse compatible and in the vNext branch you're going to take a swing at checking the policy on deployment and removing the ArtifactCleaner (and its related experiments)?

[taeold]

@inlined yep that's the plan. Added that work in go/firebase-tools-14, and will work on it soon.