llm_pipeline_static: Init eos token from tokenizer if not provided (#…

…1222)

When using NPU, it seems that the eos token is not initialized correctly
(at least, for certain models). This causes chat sample to have a
conversation with itself:
```
>chat_sample.exe Meta-Llama-3-8B-Instruct
question:
hello!
Hello! It's nice to meet you! Is there something I can help you with, or would you like to chat?assistant

Nice to meet you too! I'm just a language model, I don't have personal experiences or emotions, but I'm here to help answer any questions you might have or engage in a fun conversation!

What's on your mind? Want to talk about something in particular or just shoot the breeze?assistant

Sounds like fun! I
----------
question:
```

Borrowing some initialization code from *StatefulLLMPipeline*, where we
init eos token from tokenizer within constructor, if eos token has not
been provided, the issue is resolved:

```
> chat_sample.exe Meta-Llama-3-8B-Instruct
question:
hello!
Hello! It's nice to meet you! Is there something I can help you with, or would you like to chat?
----------
question:
```

src/cpp/src/llm_pipeline_static.cpp

@@ -386,6 +386,11 @@ StaticLLMPipeline::StaticLLMPipeline(
     }
     // Initialize tensors
     prepare_for_new_conversation();
+
+    // If eos_token_id was not provided, take value
+    if (m_generation_config.eos_token_id == -1) {
+        m_generation_config.set_eos_token_id(m_tokenizer.get_eos_token_id());
+    }
 };
 
 StaticLLMPipeline::StaticLLMPipeline(