### What this PR does / why we need it?
Fix the MTP test failure caused by accessing non-existent attribute
`forward_context.draft_attn_metadatas`.
**Root cause:**
In `AscendAttentionBackendImpl.update_graph_params`, the code
incorrectly accessed `forward_context.draft_attn_metadatas`, but
`ForwardContext` class doesn't have this attribute. The original code
passed this value via function parameter.
**Fix:**
Add `draft_attn_metadatas` parameter to the entire call chain:
- `update_full_graph_params` function in `acl_graph.py`
- All `update_graph_params` methods in attention backends
- Pass the parameter correctly in `eagle_proposer.py`
Also applied Gemini's suggestion to make `vllm_config=None` in
`AscendAttentionCPImpl.update_graph_params` for API consistency.
Related to item 9 in #5463
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
This fixes the CI test failure:
`test_deepseek_mtp_correctness[True-FULL_DECODE_ONLY-2-wemaster/deepseek_mtp_main_random_bf16]`
Signed-off-by: lico67373 <918688502@qq.com>
379ce599d0