Makes busy wait in thread pool optional to prevent unnecessary high cpu loads

[DavidPL1]

Using a thread pool with $n > 1$ workers substantially raises the CPU usage. This is mainly due to the worker queue using std::this_thread::yield right here.
Especially in a nearly idle simulation state (e.g. when pausing in Simulate-like programs), this unnecessarily increases CPU load with $n$ cores at 100% load.

My proposed solution is to introduce an option to toggle busy waiting, which would opt for std::this_thread::sleep if disabled. This would retain the option to use yield instead of sleep if speed is more important. Although, I think that sleeping should be the default fit for most use cases.

Let me know your thoughts on this