* Add unit and integration tests for `Container` activity, covering behavior such as variable scoping, child activity execution, and mixed variable types.
* Refactor `RunWorkflowAndCaptureOutput` method in `ContainerTests` for better code organization
* Move `Sequence` activity tests to a dedicated namespace and add new unit and integration tests for enhanced coverage.
- Deleted outdated `SequenceTests` and related workflows.
- Introduced `SequenceActivity` namespace with improved organization.
- Added comprehensive unit and integration test coverage for sequential execution, nested sequences, conditional breaking, variables, and dynamic activities.
* Relocate `SequenceActivity` tests to `Activities` namespace to improve organization and update references in related test classes.
* Refactor `SequenceTests` to move `DynamicSequenceWorkflow` to its own file for better test organization.
* Extract `TestContainer` to `Elsa.Testing.Shared.Activities` for reuse across test projects.
