Update find converter internal conditions and added tests

Author: andreas-grafenberger

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/DefaultAttributeConverterProvider.java

@@ -157,11 +157,11 @@ private <T> Optional<AttributeConverter<T>> findConverterInternal(EnhancedType<T
             return Optional.of(converter);
         }
 
-        if (Map.class.isAssignableFrom(type.rawClass())) {
+        if (Map.class.equals(type.rawClass())) {
             converter = createMapConverter(type);
-        } else if (Set.class.isAssignableFrom(type.rawClass())) {
+        } else if (Set.class.equals(type.rawClass())) {
             converter = createSetConverter(type);
-        } else if (List.class.isAssignableFrom(type.rawClass())) {
+        } else if (List.class.equals(type.rawClass())) {
             EnhancedType<T> innerType = (EnhancedType<T>) type.rawClassParameters().get(0);
             AttributeConverter<?> innerConverter = findConverter(innerType)
                 .orElseThrow(() -> new IllegalStateException("Converter not found for " + type));