[EPLB][Bugfix] policy_swift_balancer bugfix and renaming (#5897)

### What this PR does / why we need it?
1. Rename dynamic_ep to default_eplb.
2. Rename dynamic_ep_v2 to swift_balancer
3. Discard func compose_expert_update_info_bipartite.

- vLLM version: v0.13.0
- vLLM main:
bde38c11df

Signed-off-by: shenchuxiaofugui <1311027364@qq.com>

docs/source/developer_guide/feature_guide/eplb_swift_balancer.md

@@ -25,8 +25,8 @@ vllm_ascend
 │   ├── core
 │   │   ├── policy
 │   │   │   ├── policy_abstract.py
-│   │   │   ├── policy_dynamic_ep.py
-│   │   │   ├── policy_dynamic_ep_v2.py
+│   │   │   ├── policy_default_eplb.py
+│   │   │   ├── policy_swift_balancer.py
 │   │   │   ├── policy_factory.py
 │   │   │   ├── policy_flashlb.py
 │   │   ├── eplb_device_transfer_loader.py
@@ -52,9 +52,9 @@ vllm_ascend
   *Load balancing algorithms with factory pattern instantiation*
     - `policy_abstract.py`  
     Abstract class for load balancing strategy interfaces
-    - `policy_dynamic_ep.py`  
+    - `policy_default_eplb.py`  
     Default implementation of open-source EPLB paper algorithm
-    - `policy_dynamic_ep_v2.py`  
+    - `policy_swift_balancer.py`  
     Enhanced version optimizing expert swaps for low-bandwidth devices (e.g., A2)
     - `policy_flashlb.py`  
     Threshold-based adjustment reducing operational costs through layer-wise fluctuation detection