feat(parser): AS pipe syntax

[geooo109]

This PR adds support for the AS pipe syntax.

Operator	Implemented
FROM	✅
SELECT	✅
WHERE	✅
WHERE (replacing HAVING)	✅
WHERE (replacing QUALIFY)	✅
EXTEND
SET
RENAME
DROP
AS	✅
LIMIT	✅
AGGREGATE WITH GROUP/ORDER BY	✅
ORDER BY	✅
UNION	✅
INTERSECT	✅
EXCEPT	✅
JOIN	✅
CALL
TABLESAMPLE
PIVOT	✅
UNPIVOT	✅