Async lambdas passed to Assert.That(...) are evaluated too early #3137
Description
Lambdas passed to Assert.That(...) are intended to be evaluated during AssertionBuilder.GetAssertionData(). However async lambdas are already started when AsAssertionData() is called, which happens already during builder execution.
The underlying reason is, that when a Func is invoked to get the Task, the Task may immediately be scheduled on the thread pool.
It might be possible to wrap a Func into a ValueTask in a way that guarantees lazy evaluation, which would fix the bug. However making the laziness requirement more explicit is probably better. This way it is not only less error-prone but it should also make the code more clear.