Adds the `class DummyLLMAdapter(LLMInterface)` class for profiling of
large datasets without actual LLM calls in the top level
`profiling/util` location.
I also move the `show_prompt` implementation from the child classes to
`LLMInterface`, since the implementations were identical.
I expanded the scope to also include a DummyEmbeddingEngine.
bbaf78f54e