Allow Pinotdb client to hit v2 engine

[mndoping1]

Python's Pinotdb client version 0.4.5 (https://docs.pinot.apache.org/users/clients/python) does not support table aliasing. For example, queries such as SELECT "tbl1"."x" FROM "y" "tbl1" aren't able to run because table aliasing isn't supported. However, Pinot's v2 engine:https://docs.pinot.apache.org/developers/advanced/v2-multi-stage-query-engine allows table aliasing and we'd need the client to run against the v2 engine with table aliasing support.

[xiangfu0]

Thanks, we will add an option to allow client query v2 query engine.

[xiangfu0]

#69