Sync built images to ECR and GHCR on release

[rquitales]

Proposed changes

This PR extends #830 by enabling image synchronization during the release job. The syncing process is now more reliable, as it has been updated to use skopeo for copying. Leveraging skopeo brings the added advantage of supporting image copying across all architecture types, rather than being limited to the host machine's architecture.

An example passing run: https://github.com/pulumi/pulumi-kubernetes-operator/actions/runs/13339040901

The images are now synced to the following repositories:

• docker.io/pulumi/pulumi-kubernetes-operator
• ghcr.io/pulumi/pulumi-kubernetes-operator
• public.ecr.aws/pulumi/pulumi-kubernetes-operator

Related issues (optional)

Closes: #811
Closes: #481

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 52.25%. Comparing base (855b2b6) to head (7fa2718).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #831   +/-   ##
=======================================
  Coverage   52.25%   52.25%           
=======================================
  Files          32       32           
  Lines        4507     4507           
=======================================
  Hits         2355     2355           
  Misses       1959     1959           
  Partials      193      193           

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