Efcore: Internal code usage scenarios missed by the analyzer

[ajcvickers]

Identified scenarios:

• [x] Generic type parameter (e.g. context.GetService<IInMemoryStoreCache>())
• [x] Type usage without instantiation (IStateManager state = null)
• [x] Typeof (typeof(IInMemoryStoreCache))
• [x] private readonly field in private nested class
• [x] Implemented interface

[smitpatel]

May be because generic type check is missed?

[ajcvickers]

Also doesn't seem to detect:
```C#
IStateManager state = null;

But does detect:
```C#
IStateManager state = new StateManager(null);

[ajcvickers]

Finding more cases like this. It seems that the analyzer doesn't detect any uses of internal types/members that don't actually involve invoking anything.

[roji]

@ajcvickers have converted this issue to a shopping list of currently undetected cases in the analyzer. Let's add more to it as we find them.

[smitpatel]

private readonly field in private nested class.

[roji]

@smitpatel can you provide a bit more detail on "private readonly field in private nested class", possibly a code fragment?

[smitpatel]

public class A
{
    private class B
    {
        private readonly InternalEntityEntry Entry;
    }
}