AwaitableYieldInstruction.cs

public static class YieldInstructionExtension
{
    public static YieldInstructionAwaiter GetAwaiter(this YieldInstruction yieldInstruction)
    {
        return new YieldInstructionAwaiter(yieldInstruction);
    }
}

public class YieldInstructionAwaiter : INotifyCompletion
{
    private Action _continuation;
    private YieldInstruction _yieldInstruction;
    private bool _isCompleted;
    
    public YieldInstructionAwaiter(YieldInstruction yieldInstruction)
    {
        SOME_AVAILABLE_COROUTINE_RUNNER.StartCoroutine(WaitFor(yieldInstruction));
    }

    private IEnumerator WaitFor(YieldInstruction yieldInstruction)
    {
        yield return yieldInstruction;
        _isCompleted = true;
        _continuation();
    }

    public bool IsCompleted => _isCompleted;

    public void GetResult() { }

    public void OnCompleted(Action continuation)
    {
        _continuation = continuation;
    }
}

// Example:
// await new WaitForSeconds(1f);