Support Eagle2 for Triton backend

[ispobock]

Motivation

Support Eagle2 for Triton backend and achieve 2.6x speedup on batch size 1 for no cuda graph setting. (Based on #3317, #3309, #3292)
CUDA graph will be supported in follow-up PR.

python3 -m sglang.launch_server --model meta-llama/Llama-2-7b-chat-hf --disable-radix --disable-cuda-graph --attention-backend triton

speed: 71.34 token/s

python3 -m sglang.launch_server --model meta-llama/Llama-2-7b-chat-hf  --speculative-algo EAGLE --speculative-draft lmzheng/sglang-EAGLE-llama2-chat-7B --speculative-num-steps 5 --speculative-eagle-topk 8 --speculative-num-draft-tokens 64 --mem-fraction 0.8 --disable-radix --disable-cuda-graph --attention-backend triton

speed: 185.54 token/s

Test script is referenced from #2150.

Thanks @aspctu for helping debug!