Using custom env with stdexec::task

[maxbachmann]

It's unclear to me how I can use a custom env as the second template parameter in stdexec::task and query it from inside the coroutine. For exec::task there is a sample using a context that works in the tests. However for stdexec::task I couldn't figure out how to achieve this.

Specifically I am attempting to use a custom env type that has a delegation_scheduler I can query from inside the task.