Clickhouse: Rewrite integration tests and clickhouse-test script to python 3.

[alexey-milovidov]

[bharatnc]

@alexey-milovidov I think I can take a stab at this (probably assign to me?)

[alexey-milovidov]

Azat already started working on it: https://github.com/ClickHouse/ClickHouse/pull/15007

[bharatnc]

Azat already started working on it: #15007

@alexey-milovidov I did start work on it, but looks like @azat has made more progress on this. You can probably assign this task to him? Thanks!