[Doc][KV Pool]Revision KV Pool User Guide (#7434)

### What this PR does / why we need it?
Revise the KV Pool user guide:
1. Revise Mooncake environment variables and kvconnector extra configs.
2. Delete `use_ascend_direct` in kv connector extra config as it is
deprecated
3. Delete `kv_buffer_device` and `kv_rank` in P2P mooncake config
4. Unifies default `max-model-len` and `max-num-batch-tokens` in
examples given.

### Does this PR introduce _any_ user-facing change?

### How was this patch tested?

- vLLM version: v0.17.0
- vLLM main:
4497431df6

---------

Signed-off-by: Pz1116 <zpbzpb123123@gmail.com>
Co-authored-by: Chao Lei <leichao139636@163.com>

docs/source/tutorials/models/Qwen3-235B-A22B.md

@@ -448,7 +448,6 @@ vllm serve vllm-ascend/Qwen3-235B-A22B-w8a8 \
 "kv_port": "30000",
 "engine_id": "0",
 "kv_connector_extra_config": {
-      "use_ascend_direct": true,
       "prefill": {
             "dp_size": 2,
             "tp_size": 8
@@ -513,7 +512,6 @@ vllm serve vllm-ascend/Qwen3-235B-A22B-w8a8 \
 "kv_port": "30100",
 "engine_id": "1",
 "kv_connector_extra_config": {
-      "use_ascend_direct": true,
       "prefill": {
             "dp_size": 2,
             "tp_size": 8
@@ -579,7 +577,6 @@ vllm serve vllm-ascend/Qwen3-235B-A22B-w8a8 \
 "kv_port": "30100",
 "engine_id": "1",
 "kv_connector_extra_config": {
-      "use_ascend_direct": true,
       "prefill": {
             "dp_size": 2,
             "tp_size": 8