Consider inheritance when checking models

We should be able to leverage inheritance when writing models for librarys. E.g., Collections.toArray(T[]) is specified to throw an NPE whenever the parameter is null. Right now, we need to add a model for Collections.toArray, ArrayDeque.toArray, LinkedList.toArray, etc. to get full safety. It'd be nice to just add a model for Collections.toArray and then catch this for any overriding method. Would need to be careful about performance when implementing this.

Start by tracing how models for Collections.toArray and overriding methods such as ArrayDeque.toArray and LinkedList.toArray are represented and checked. Review the existing model-handling entry points and consider the performance implications called out in the issue. Done means a model for Collections.toArray provides the expected null-safety behavior for overriding methods without unacceptable performance cost.