[Misc] improve example mlpspeculator and llm_engine_example

[reidliu41]

For llm_engine_example

• add description
• add print line to separate each print

For mlpspeculator

• add description and note (not support in v1)

    raise NotImplementedError(
NotImplementedError: VLLM_USE_V1=1 is not supported with Speculative Decoding.

• format the output

from:
.73 seconds
With speculation
Processed prompts: 100%|█| 1/1 [00:03<00:00,  3.54s/it, est. speed input: 12.73 toks/s, output: 44.9
Processed prompts: 100%|█| 1/1 [00:03<00:00,  3.00s/it, est. speed input: 14.98 toks/s, output: 52.9
Processed prompts: 100%|█| 1/1 [00:03<00:00,  3.00s/it, est. speed input: 14.99 toks/s, output: 52.9
0.018888232093187247
text: 'The current president of the United States is Joe Biden. He was inaugurated on January 20, 2021, and is serving his first term in office. Prior to his presidency, Biden served as Vice President under Barack Obama from 2009 to 2017. He has a long history of public service, including serving in the Senate for six terms from 1973 to 2009. Biden has been a strong advocate for progressive policies, including expanding access to healthcare, addressing climate change, and advancing civil rights. He has also been a vocal critic of President Donald Trump and has sought to undo many of the policies enacted during his presidency.'
[rank0]:[W407 16:14:49.860801583 ProcessGroupNCCL.cpp:1496] Warning: WARNING: destroy_process_group() was not called before program exit, which can leak resources. For more info, please see https://pytorch.org/docs/stable/distributed.html#shutdown (function operator())

to:
Processed prompts: 100%|█| 1/1 [00:03<00:00,  3.01s/it, est. speed input: 14.97 toks/s, output: 52.9
--------------------------------------------------
With speculation
time:  0.018905594663799933
text: 'The current president of the United States is Joe Biden. He was inaugurated on January 20, 2021, and is serving his first term in office. Prior to his presidency, Biden served as Vice President under Barack Obama from 2009 to 2017. He has a long history of public service, including serving in the Senate for six terms from 1973 to 2009. Biden has been a strong advocate for progressive policies, including expanding access to healthcare, addressing climate change, and advancing civil rights. He has also been a vocal critic of President Donald Trump and has sought to undo many of the policies enacted during his presidency.'
--------------------------------------------------
[rank0]:[W407 16:59:03.109660286 ProcessGroupNCCL.cpp:1496] Warning: WARNING: destroy_process_group() was not called before program exit, which can leak resources. For more info, please see https://pytorch.org/docs/stable/distributed.html#shutdown (function operator())

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[DarkLight1337]

Thanks for cleaning this up!