Multiple improvements

Improve IbisExecutionEngine, refactor ExecutionEngine, fix bugs (#416)

* Improve IbisExecutionEngine

* update

* lint

* Update ray configs

* update

* Add is_distributed

* make ibis handle timestamp

* refactor execution engine

* update import

* add plot extension

* fix tests

* fix tests

* update dependency

* make fsql dialect configurable

* add dialect

* fix tests, update dataframe interface

* use more df.columns instead of df.schema

* ibis handle unsupported types

* update

* update

* yield table

* update

* update

* fix seed for fsql

* refactor ibis engine

* update