The code change deletes the line where the messageInput is added to the Inputs list of the builder in the `Workflows.cs` file, since this operation is redundant. The input is automatically added during its creation and doesn't need an explicit addition, thus improving code efficiency.
Implemented new integration tests for serialization of programmatic workflows. Additionally, major refactoring was performed on the serialization classes. This involved moving the classes to new namespaces and enhancing their functionalities to correctly handle null inputs and to support the serialization of activities and expressions. Also, updated Elsa.sln.DotSettings and JsonActivitySerializer to handle new serializers.
