DuckDB, PostgreSQL, SQLite: Support window-frame EXCLUDE

[corasaurus-hex]

What is this?

Adds support for window-frame EXCLUDE in the DuckDB, PostgreSQL, SQLite, and Generic dialects.

SELECT sum(n) OVER (ORDER BY n ROWS UNBOUNDED PRECEDING EXCLUDE CURRENT ROW) FROM t;
SELECT sum(n) OVER (ORDER BY n ROWS UNBOUNDED PRECEDING EXCLUDE GROUP) FROM t;
SELECT sum(n) OVER (ORDER BY n ROWS UNBOUNDED PRECEDING EXCLUDE TIES) FROM t;
SELECT sum(n) OVER (ORDER BY n ROWS UNBOUNDED PRECEDING EXCLUDE NO OTHERS) FROM t;

Introduced in DuckDB 0.10.0, PostgreSQL 11, and SQLite 3.28.0.