[SpecDecode] Fix Draft model proposer (#7230)

### What this PR does / why we need it?
This pr fix the Unified draft parallel feature. 
1. In Draft model proposer, there are exceed 1 attention layers in
target model, thus removing the assertion on layer number.
2. we should get block size through `draft_attn_groups` instead of
`attn_metadata_builder` after 0.17.0.
3. `attn_update_stack_num_spec_norm` shouldn't be done when unified
draft parallel is enabled

### How was this patch tested?
Test pass with
`tests/e2e/singlecard/spec_decode/test_v1_spec_decode.py::test_parallel_drafting_acceptance`,
which is already included in CI

- vLLM version: v0.17.0
- vLLM main:
4034c3d32e

Signed-off-by: MengqingCao <cmq0113@163.com>

vllm_ascend/worker/model_runner_v1.py

@@ -74,7 +74,6 @@ from vllm.v1.outputs import (
 from vllm.v1.sample.logits_processor import build_logitsprocs
 from vllm.v1.sample.metadata import SamplingMetadata
 from vllm.v1.sample.rejection_sampler import RejectionSampler
-from vllm.v1.spec_decode.draft_model import DraftModelProposer
 from vllm.v1.spec_decode.metadata import SpecDecodeMetadata
 from vllm.v1.structured_output.utils import apply_grammar_bitmask
 from vllm.v1.utils import record_function_or_nullcontext
@@ -2561,7 +2560,7 @@ class NPUModelRunner(GPUModelRunner):
             if self.speculative_config and (
                 self.speculative_config.use_eagle() or self.speculative_config.uses_draft_model()
             ):
-                assert isinstance(self.drafter, AscendEagleProposer | DraftModelProposer)
+                assert isinstance(self.drafter, AscendEagleProposer | AscendDraftModelProposer)
                 self.drafter.initialize_attn_backend(kv_cache_config, self.kernel_block_sizes)
 
         if has_kv_transfer_group():