Add shared search executor

[MochiXu]

The approach to integrating Tantivy with ClickHouse is as follows:
A ClickHouse Table will have multiple DataParts, each with its own Tantivy index. However, I would like ClickHouse to share a thread pool among different DataParts during concurrent searches, in order to reduce resource overhead during the search process. I have created a bridging repo(tantivy-search) between Tantivy and ClickHouse.

The code for using a shared thread pool can be referred to at this link.

[fulmicoton]

Merged! Just to put it in your radar, Quickwit can be used to search into Clickhouse.