Add verbose parameter for llamacpp (#7253)

**Title:** Add verbose parameter for llamacpp

**Description:**
This pull request adds a 'verbose' parameter to the llamacpp module. The
'verbose' parameter, when set to True, will enable the output of
detailed logs during the execution of the Llama model. This added
parameter can aid in debugging and understanding the internal processes
of the module.

The verbose parameter is a boolean that prints verbose output to stderr
when set to True. By default, the verbose parameter is set to True but
can be toggled off if less output is desired. This new parameter has
been added to the `validate_environment` method of the `LlamaCpp` class
which initializes the `llama_cpp.Llama` API:

```python
class LlamaCpp(LLM):
    ...
    @root_validator()
    def validate_environment(cls, values: Dict) -> Dict:
        ...
        model_param_names = [
            ...
            "verbose",  # New verbose parameter added
        ]
        ...
        values["client"] = Llama(model_path, **model_params)
        ...
```
---------

Signed-off-by: teleprint-me <77757836+teleprint-me@users.noreply.github.com>

langchain/llms/llamacpp.py

@@ -103,6 +103,9 @@ class LlamaCpp(LLM):
     streaming: bool = True
     """Whether to stream the results, token by token."""
 
+    verbose: bool = True
+    """Print verbose output to stderr."""
+
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that llama-cpp-python library is installed."""
@@ -121,6 +124,7 @@ class LlamaCpp(LLM):
             "n_batch",
             "use_mmap",
             "last_n_tokens_size",
+            "verbose",
         ]
         model_params = {k: values[k] for k in model_param_names}
         # For backwards compatibility, only include if non-null.