* 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.
Eliminated the `Elsa.Labels`, `Elsa.Environments`, and `Elsa.OpenTelemetry` modules along with their handlers, contracts, models, and related functionality. This cleanup improves maintainability and aligns the codebase with recent architectural changes.
