Diagnostics run await.delay() too often

[emmericp]

#2664 got a 25% speed increase by disabling await.delay() for the non-interactive use case.

Many diagnostics call await.delay() for every single ast node they check, so running all diagnostics on a file will probably reschedule the thread more than once per node which is a significant overhead.

I guess fully removing it for the interactive use case isn't a great solution, but maybe there is some kind of middleground like only rescheduling only every n calls?

[emmericp]

Note: this is likely not directly related to #2660, because that bug is about a slowdown that is way worse than only 25%