RFC - Retention policies

The upcoming version of Octopus will introduce retention policies to manage the number of releases and deployments retained, optimizing disk space usage and enhancing performance. These policies will integrate with the Project Groups feature, allowing configuration across similar projects without redundancy, and will determine when Release, Deployment, and Task objects are removed from the RavenDB database. The policy settings cater to various scenarios, such as deleting unused releases after a week or retaining deployed releases longer. Tentacles will have a setting based on the number of deployments to manage extracted package folders, avoiding the need for scheduled cleanup jobs. Additionally, NuGet packages will automatically be cleaned every 12 hours for packages older than three days, with re-downloads facilitated through the NuGet server. Feedback is sought to ensure the feature remains powerful yet simple, and input on whether project groups are the appropriate level for defining retention policies is requested.