On-demand out of order execution of stages

Stages in a pipeline have dependencies and some stages are un-skippable. However, there are scenarios where one would want to start a future stage more quickly than wait for all its dependencies. Examples of such scenarios are (a) fast-track a hot fix and (b) ramp up the traffic to a service faster than the pipeline normally allows (in this case, each stage models a certain amount of ramp-up traffic). We will allow this provided (a) the stage you want to start does not have any un-skippable stages in its dependency chain and (b) you have the permission to start a stage out of order.