### What this PR does / why we need it?
LayerwiseConnector supports the virtual push functionality on node D.By
adding a do_virtual flag to request metadata, the system can now
identify and process certain requests virtually, bypassing the actual KV
cache transfer process. This allows for immediate completion of these
requests from the consumer's perspective, potentially enabling
optimizations or specific testing scenarios where physical data transfer
is not required.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
By ci
- vLLM version: v0.17.0
- vLLM main:
4034c3d32e
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Signed-off-by: wangxiaoteng <wangxiaoteng@huawei.com>
c7157af8f7