Dry-run policy execution 'savepoint' - restart policy dry-run from the 'saved' place

[anvabr]

Problem description

In practice when developing a policy it is often rerun (in dry-run mode) to test latest changes. For realistic policies it can be time consuming as they tend to be quite lengthy and complex and thus require to remember and then re-execute all operations just to reach the point which is tested. It can be inconvenient and time consuming.

Note: this is different from #2559 which targets Guardian DR, i.e. its subject is published artefacts while this ticket aims to simplify dry-run (i.e. policy authoring) mode.

Requirements

• Introduce a new functionality for users to 'save' dry-run execution status at arbitrary point by clicking 'save state' button.
• The system should support multiple iterations of creation/deletion of a savepoint for the same execution workflow
• Next time the (draft) policy is executed in the dry-run mode users should be given a choice whether to restart from the beginning, or continue execution from the 'savepoint'.

Definition of done

• Dry-run savepoint functionality is implemented as above
• Documentation is updated accordingly

Acceptance criteria

UX of policy authoring is improved by giving users ability to restart dry-run policy execution from the last savepoint. They should be able to reset a savepoint to a new place following such a restart.

[dubgeis]

@prernaadev01 Request from Bram to move this up to discuss in refinement for timing.