### What this PR does / why we need it?
1.In short, we renamed the existing MooncakeStoreConnector to
AscendStoreConnector and extracted the storage engine interaction logic
into a new Backend class.
Associated RFC：https://github.com/vllm-project/vllm-ascend/issues/4329
2.Fixed the issue where the number of input parameters for the connector
was incorrect, introduced in vllm 0.11.2
### Does this PR introduce _any_ user-facing change?
change MooncakeStoreConnector to AscendStoreConnector
### How was this patch tested?
- vLLM version: v0.11.2
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Signed-off-by: fems14 <1804143737@qq.com>
### What this PR does / why we need it?
- global_segment_size and local_buffer_size use constants for unified
management.
- Newly added support for input formats ending with GB, MB, KB, and B,
while being compatible with existing input methods.
### Does this PR introduce _any_ user-facing change?
- Users can use new input methods
- The documentation has also been modified
### How was this patch tested?
- vLLM version: v0.11.0
- vLLM main:
83f478bb19
---------
Signed-off-by: 李子琦 <liziqi_ing@163.com>
