Add hf_transfer to testing image (#10096)

Dockerfile

@@ -191,6 +191,11 @@ ADD . /vllm-workspace/
 RUN --mount=type=cache,target=/root/.cache/pip \
     python3 -m pip install -r requirements-dev.txt
 
+# enable fast downloads from hf (for testing)
+RUN --mount=type=cache,target=/root/.cache/pip \
+    python3 -m pip install hf_transfer
+ENV HF_HUB_ENABLE_HF_TRANSFER 1
+
 # Copy in the v1 package for testing (it isn't distributed yet)
 COPY vllm/v1 /usr/local/lib/python3.12/dist-packages/vllm/v1