Introduce fused MoE kernel

[kozistr]

Change Log

related to huggingface/text-embeddings-inference#717

Thanks to all the following resources, I was able to complete implementing these and adapting to TEI :) (+ I've tested that it's working)

• topk_softmax kernel from vLLM
• fused MoE kernel from here
  • Qwen3 MoE
  • Nomic MoE

Also, I'm very new to CUDA programming, so any feedback or suggestions would be greatly appreciated 🤗

@Narsil @alvarobartt @EricLBuehler