How to exclude PHP Core classes?

Support Question

I want to protect my domain from classes outside namespace but not the PHP core classes, e.g. \DateTimeImmutable etc.
How to I do that globally? I can exclude them for example passing then to NotHaveDependencyOutsideNamespace as second argument, but that's to much overhead.

[veylor-fp]

Same with vendor code,
for now we're using a whitelist which will become unmanageable over time

[mxr576]

PHP Core classes would be also an interesting question to me, like \DateTimeImmutable or \RuntimeException. Should they be excluded by default?