Add .get_task method to Schedulers - APS v4

### Things to check first

- [X] I have searched the existing issues and didn't find my feature already requested there

### Feature description

Hello,

My suggestion is to add the .get_task(task_id=...) method to the Schedulers.

### Use case

I found myself in a situation where I needed to pass the Task instance directly to the .add_job method to get an existing task configuration.

I could use the method to get all tasks with .get_tasks. But I would have to filter this list every time to get a single specific task. I don't think this would be a very interesting approach in my use case and I believe my suggestion will be useful to others as well.