[RFE] Support Speculative Decoding

[okdimok]

I see SpecDec being by default enabled in all the production installations. I see some mentions of eagle and MTP in the code, but no documentation and/or example. I think it might change the outcome, regarding the recommended hyperparameters.

[Arsene12358]

For the time being I think eagle MTP is only available for DeepSeek V3. We do plan to redesign this part and provide a more comprehensive support in the future