update flashinfer to v0.2.9rc1

[weireweire]

Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.

Purpose

updata flashinfer and modify it's trtllm-gen call to use latest API.

Test Plan

test llama4 with lm_eval

Test Result

|Tasks|Version|     Filter     |n-shot|  Metric   |   |Value|   |Stderr|
|-----|------:|----------------|-----:|-----------|---|----:|---|-----:|
|gsm8k|      3|flexible-extract|     5|exact_match|↑  |0.934|±  |0.0111|
|     |       |strict-match    |     5|exact_match|↑  |0.912|±  |0.0127|

(Optional) Documentation Update

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.

💬 Join our developer Slack at https://slack.vllm.ai to discuss your PR in #pr-reviews, coordinate on features in #feat- channels, or join special interest groups in #sig- channels.

Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can either: Add ready label to the PR or enable auto-merge.

🚀

[gemini-code-assist]

Code Review

This pull request updates the FlashInfer dependency to version v0.2.9rc1. The code changes correctly adapt the calls to trtllm_batch_decode_with_kv_cache to match the updated API in the new version. The changes are consistent across the affected files and appear to be correct.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @weireweire.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

[mgoin]

Aren't there other updates needed for the latest release? I remember the flashinfer fp4 moe utils also have some changes cc @wenscarl

[mgoin]

LGTM. Other related PRs for this change have already landed:
Update flashinfer CUTLASS MoE Kernel #21408
Fix vLLM cutlass FP4 MoE functionality issue #21465

[wenscarl]

#21408 is already merged. No more changes needed.