feat: Support padding tokens with seqlen=0 for rope+quant+kv cache update fusion kernel#2792

elvischenv wants to merge 2 commits intoflashinfer-ai:mainflashinfer-ai/flashinfer:mainfrom

elvischenv:elvischenv/support-rope-fusion-token-paddingelvischenv/flashinfer:elvischenv/support-rope-fusion-token-paddingCopy head branch name to clipboard