fix triton token2wav model cache thread unsafety

[GoyoUijin]

If the user does not explicitly specify a request_id in the Triton client, the Triton server sets request_id=''.
In this case, different threads may write to the same key in CosyVoice2Model.hift_cache_dict simultaneously, causing cache data from different requests to be mixed up.
When serving CosyVoice2 via Triton Server, I actually observed that the output audio from different requests got mixed.

Example

On the client side:

# request_id is not explicitly specified
sync_triton_client.async_stream_infer(
    "cosyvoice2",
    inputs,
    outputs=outputs,
    enable_empty_final_response=True,
)

On the server side:

    def execute(self, requests):
        for request in requests:
            request_id = request.request_id()  # This value is ''

Therefore, I propose generating and using a unique uuid directly on the server side, instead of relying on the user to provide a request_id.

[yuekaizhang]

@GoyoUijin Many thanks. @aluminumbox Would you mind helping merge the PR?