In GetOrAddAsync replace Thread.Yield by await Task.Delay(1)?

[szmcdull]

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Is your feature request related to a problem? Please describe.
Thread.Yield in a loop will lock down the whole thread, so no other async routines can run on the trhead. This may lead to problems where many async routines are running or being created.

Describe the solution you'd like
Simply replace Thread.Yield by await Task.Delay(1) or something alike.

Additional context
I'm specifically concern because I'm using a single-threaded async model. Locking the thread will dead lock.