Use spammable_entity_type when setting type for generic spammable

What does this MR do and why?

This MR uses the spammable_entity_type to set the type for a generic spammable. The current functionality has several different types depending on the class name (i.e. DiscussionNote, DiffNote, Note, etc). Using spammable_entity_type assign these different classes to the same type.

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