Support for checking the namespace exactly

### Feature Request

|    Q        |   A
|------------ | ------
| New Feature | yes
| RFC         | no
| BC Break    | no

#### Summary

Currently (AFAIK) the only way to verify namespaces is `ResidesInTheseNamespaces` which is always recursive. There's use cases where we want to check the namespace **exactly**, for example `App\Entity`, not `App\Entity\Whatever`.