CA2257 should not be reported on nested types #7106

Analyzer

Diagnostic ID: CA2257: Members defined on an interface with the 'DynamicInterfaceCastableImplementationAttribute' should be 'static'

Analyzer source

SDK: Built-in CA analyzers in .NET 8 SDK or later

Version: SDK 8.0.100

Describe the bug

The analyzer reports that nested types in a type with [DynamicInterfaceCastableImplementation] should be static, but the rationale for that rule does not apply to nested types.

Steps To Reproduce

interface Foo
{
   void Bar();
}

[DynamicInterfaceCastableImplementation]
interface FooImpl
{
     void Foo.Bar() {}

     private class C {}
}

Expected behavior

No diagnostic

Actual behavior

A diagnostic on the class declaration

Additional context