TextStreamer: An option to print / put every single token instead of whole words

### Feature request https://github.com/huggingface/transformers/blob/v4.37.2/src/transformers/generation/streamers.py#L108-L114 The current implementation forces us to visualize decoding on a per word basis. Add an option to print the string as soon as it's generated. ### Motivation I use TextStreamer to visualize several things in my terminal: 1. How words are split 2. Actual token-per-second performance 3. Understand how it generates very long words like URLs ### Your contribution I'm a Python noob