[refactor] refactor deepseek-related files (#2849)

### What this PR does / why we need it?
This PR deletes ~2K lines of code about deepseek modeling. It falls back
CustomDeepseekV2 modules to original vllm implementations and adapts
some modifications in vllm about deepseek and moe.
### Does this PR introduce _any_ user-facing change?
No.
### How was this patch tested?
E2E  vllm serving with torchair graph mode and eager mode.

- vLLM version: v0.10.2
- vLLM main:
759ef49b15

---------

Signed-off-by: linfeng-yuan <1102311262@qq.com>
Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>
Co-authored-by: yiz-liu <136800916+yiz-liu@users.noreply.github.com>
Co-authored-by: Yizhou Liu <liu_yizhou@outlook.com>

vllm_ascend/torchair/torchair_worker.py

@@ -32,9 +32,10 @@ class NPUTorchairWorker(NPUWorker):
         """Override determine_available_memory to use cached torchair kv_cache_bytes."""
 
         available_kv_cache_memory = super().determine_available_memory()
-
-        if get_ascend_config(
-        ).torchair_graph_config.use_cached_kv_cache_bytes and check_kv_cache_bytes_cache_exist(
+        ascend_config = get_ascend_config()
+        if ascend_config.enable_shared_expert_dp:
+            return available_kv_cache_memory
+        if ascend_config.torchair_graph_config.use_cached_kv_cache_bytes and check_kv_cache_bytes_cache_exist(
         ):
             old_kv_cache_bytes = read_kv_cache_bytes_from_file(
                 torch.distributed.get_rank())