Add a get_run_state function at application level

### 📝 Description of the feature

If you use

`osl.application.project.start(wait_for_finished=False)`

you want to have a way of checking if the run finished.

My current approach of polling
`while True:
status = osl.project.root_system.get_status()
if status == "Processing done":
print(f'status: {status}')
break
elif status == "Check failed":
print(f'status: {status}')
break`

does work, but it comes to timing issues when I activate/deactivate certain nodes and call again

`osl.application.project.start(wait_for_finished=False)`

The issue I noticed is, that the second `start` call does nothing - my assumption, the first start is not yet at end even though the status is already Processing done.

### 💡 Steps for implementing the feature

I want to call a function that returns the run state of the application / system based on the same notification system that is used when I call

`osl.application.project.start(wait_for_finished=True)`

### 🔗 Useful links and references

[proxy_solver_amop_opt_on_amop_validation.txt](https://github.com/user-attachments/files/17960026/proxy_solver_amop_opt_on_amop_validation.txt)