* Restore EF Core persistence layer
Originally, we had moved EF Core to the extensions repo, but in practice this turned out to be rather impractical when debugging elsa-core, given that we would lose all of the state (workflow definitions, instances, etc.) across application restarts.
* Integrate PostgreSQL support into EF Core persistence and enhance BlobStorage workflows provider setup.
Introduced a new `Cancel` alteration type with its corresponding handler to allow workflow instance cancellations in alteration plans. Updated related services, serialization configurations, and activity metadata to support the new type. Improved JSON polymorphism handling to include the `Cancel` type.
* Implement Alteration types and engine
* Implement Alteration APIs
* Refactor activity work item with support for activity input
* Serialize scheduled activities as part of workflow state
* Add signal to schedule child activity
* Implement stores for plans and jobs
* Add EF Core provider
* Add Retry endpoint
* Keep root context as always active. The root context is the workflow execution context and contains persistent variable state
* Regenerate EF Core migrations
* Handle orphaned activity execution contexts
* Refactor workflow execution factory
* Enable configuring Jint from Program
* Update ModifyVariable alteration with support for type deserialization
* Use ShortGuid for identity
* Cleanup WorkflowServer host
