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