### What this PR does / why we need it?
Current mooncake connector has following problems with PP and MTP
enabled:
1. MTP layer kv caches are not transfered, it may cause decreasing of
accept ratio: This PR add MTP layer indices for last PP stage after
calculating end_layer in transfer_kv_cache
2. While MTP enabled, PP layers divided by default may cause imbalance
between stages, we need to use `VLLM_PP_LAYER_PARTITION` environment to
make it balance by hand, but in mooncake connector kv transfer, decode
doesn't know the partition of prefill node: This PR add config
`pp_layer_partition` in `kv_connector_extra_config` to make decode node
acquire the partition information of prefill node.
### Does this PR introduce _any_ user-facing change?
When prefill using `VLLM_PP_LAYER_PARTITION` environment, add
`pp_layer_partition` in `kv_connector_extra_config` like below:
```
export VLLM_PP_LAYER_PARTITION=33,28
"kv_connector_extra_config": {
"use_ascend_direct": true,
"prefill": {
"dp_size": 1,
"tp_size": 8,
"pp_size": 2,
"pp_layer_partition": "33,28"
},
"decode": {
"dp_size": 16,
"tp_size": 1,
"pp_size": 1
}
}
```
### How was this patch tested?
- vLLM version: v0.12.0
- vLLM main:
ad32e3e19c
---------
Signed-off-by: lidenghui <lidenghui1110@gmail.com>
332b547728