Update optimizer to avoid reducing subqueries with WHERE

[plypaul]

This PR updates SqlRewritingSubQueryReducer to avoid reducing subqueries when there is a WHERE clause and there are column identifier changes. For example:

-- src2
SELECT
  src1.bookings AS bookings
  , src1.ds AS ds
FROM (
  -- src1
  SELECT
    src0.bookings AS bookings
    , src0.created_at AS ds
  FROM demo.fct_bookings src0
) src1
WHERE ds >= "2020-01-01"

->

-- Potential error
SELECT
  src0.bookings AS bookings
  , src0.created_at AS ds
FROM demo.fct_bookings src0
WHERE  ds >= "2020-01-01"

Due to the evaluation of the WHERE clause before the column expressions in some SQL engines, the example above would have produced an error.