[Refactor] move the metadata from attention_v1 to util(ready for extract common_cp) & realize Ascendmetadata inherit from the parent class. (#5203)

RFC: https://github.com/vllm-project/vllm-ascend/issues/4629

1. Remove the pcp-related code from attention_v1.
2. Establish the inheritance relationship of CommonAttentionMetadata.

TODO
1. extract common_cp
2. move cp metadata to common_cp.
3. remove commonAttentionMetadata for aclgraph.

- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c

---------

Signed-off-by: weijinqian_v1 <weijinqian@huawei.com>
Co-authored-by: weijinqian_v1 <weijinqian@huawei.com>

tests/ut/attention/test_attention_v1.py

@@ -117,7 +117,8 @@ class TestAscendAttentionMetadataBuilder(TestBase):
             spec_attn_mask=None,
             attn_state=AscendAttentionState.ChunkedPrefill,
             num_computed_tokens_cpu=None,
-            seq_lens=None)
+            seq_lens=None,
+            max_seq_len=6)
         mock_model = MagicMock()
 
         self.builder.build(1, common_attn_metadata, mock_model)