Prevent container image overwrites with immutable tags in Bitbucket Packages

Introduces immutable tags for the Bitbucket Packages container registry. This feature allows workspace admins to configure container image tags to be protected from being overwritten, moved, or modified after their initial push. Options include protecting no tags, all tags, or specific tags based on custom RE2 regular expression rules. This enhances reproducibility, reduces deployment risk, and supports compliance requirements.