Retention Module

[Sverre-W]

I've ported the retention module from Elsa V2 to V3.

Usage is similar to before:

        elsa
            .UseRetention(options =>
            {
                options.ConfigureCleanupOptions = cleanUp =>
                {
                    cleanUp.TimeToLive = TimeSpan.FromDays(7);
                    cleanUp.SweepInterval = TimeSpan.FromHours(12);
                    cleanUp.WorkflowInstanceFilter = new WorkflowInstanceFilter
                    {
                        WorkflowStatus = WorkflowStatus.Finished
                    };
                };
            })

To be able to change the configured WorkflowInstanceFilter to add the time to live filter, I also made WorkflowInstanceFilter implement IClonable to make a deep clone of the filter.

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This change is