Implement textual export of StateUsage and StateDefinition

Implement the textual export for `StateUsage` and `StateDefinition`.

The target for this issues is https://github.com/Systems-Modeling/SysML-v2-Release/blob/master/sysml/src/examples/Simple%20Tests/StateTest.sysml without the `TransitionUsage`.

<img width="4280" height="1408" alt="Image" src="https://github.com/user-attachments/assets/58216338-5a29-47a7-9a43-e522e1869b2b" />