Add support of bulk load for the string like HBase bulkload

### Motivation

Many scenarios need to bulk-load mass data regularly, and it may bring heavy workload and latency spike if loads through the API interface. So it will be better if we can offer a way to mitigate this issue.

### Solution

We can use [RocksDB Ingest SST](https://github.com/EighteenZi/rocksdb_wiki/blob/master/Creating-and-Ingesting-SST-files.md) to bulk load those data and support for simple strings only.

see more discussions in https://github.com/apache/kvrocks/discussions/1628

Start by reading the linked RocksDB Ingest SST documentation and the discussion at apache/kvrocks#1628 to understand the proposed bulk-load workflow. Trace how simple string data currently enters Kvrocks through its API, then define completion as a supported bulk-load path that uses SST ingestion while reducing the workload and latency of repeated mass loads.

Written by the indexing model from the issue text.