✨ `OR` to `UNION` optimizer strategy

[joocer]

rewrite queries with complex OR segments as UNIONed queries.

as a contrived example:

SELECT * FROM $planets WHERE (id = 1) OR (name = 'Earth')

can be written as

SELECT * FROM $planets WHERE id = 1
UNION
SELECT * FROM $planets WHERE name = 'Earth'

Removing the OR condition is more likely to result in predicates being pushed, although will cost having to read the datasets twice (which can be quite expensive)