Allow notebook_launcher to launch to multiple GPUs from Colab (#2561)
* changed notebook_launcher to not ignore num_processes parameter on colab
* clarified documentation on notebook_launcher (that config file is ignored by notebook_launcher)
* simplified logic in launcher to retain prev elif, imported get_gpu_info from environment
* run quality and style fixes
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Co-authored-by: Zach Mueller <muellerzr@gmail.com>