Close https://github.com/flutter/flutter/issues/126303

When I encounter bugs in production environment saying null pointer error on `return _size!`, I wish I could know more information! However, currently the information is revealed by `assert(hasSize, 'RenderBox was not laid out: $this');`, thus *only* in debug mode can I know what is `this` (and/or more information that can be added), while in release mode I can only see a stack trace saying it is `RenderBox.size` that throws - nothing more :/

Therefore, it is intuitive to add this extra information in release mode. However, will it affect performance? We all know this is in critical path and should be quite careful. Thus I did some experiments: https://godbolt.org/z/zPPPf5969 From my naive understanding of assembly, the two versions of code (`size!` vs `size ?? throw`) has the same assembly, except that they throw different types of errors. In other words, when there is no error, both code should be equivalent; when there is an error, surely the new code will be slower since it calls `this.toString()`, but the error handling process is rare and already heavy, so this is not a problem.

![image](https://user-images.githubusercontent.com/5236035/236962182-b9450d59-a2ac-426f-8300-3c7edcadf35e.png)