check usage of checkpoints

We have used checkpoints in some of our plans and plan stubs where instead we might have wanted to use https://github.com/bluesky/bluesky/blob/main/src/bluesky/preprocessors.py#L717 instead. 

An example of this is the `call_sync()` and `call_qt_aware()`  stubs, but `polling_plan` might want to use it too. 

