Added db-generator Tool for Random Database Generation

Why it matters

This feature helps to reproduce issues in ClickHouse by generating randomized data that matches the structure and conditions of given SELECT queries, which is particularly useful when bug reports are incomplete or lack sufficient data for debugging.

How to use it

Use the db-generator tool by providing it with relevant SELECT queries. The tool will generate random data conforming to these queries to create a database that can be used for testing and reproducing issues.