fix(pretty-print): keep negative constants and FROM casts valid with castStyle=operator

[RaphaelFakhri]

With castStyle: "operator", the formatter changed the meaning of two kinds of casts.

A negative numeric constant lost its parentheses. CAST(-2147483648 AS int) became -2147483648::int, which casts 2147483648 first and fails with integer out of range. CAST(-12345 AS money) became -12345::money, a negation of a cast instead of a cast of a negative constant.

A cast used as a table function in FROM was written as ::. FROM CAST(1 + 2 AS int) AS a became FROM (1 + 2)::int AS a, which is a syntax error. The safety check rejected both outputs, so the statements were left unformatted.

select cast(-2147483648 as int), cast(-1.5 as numeric);
select * from cast(1 + 2 as int) as a, rows from (cast('x' as text)) as b;

This change parenthesizes a negative numeric constant before ::, and always emits CAST(...) for a cast that is a FROM item, including inside ROWS FROM. It adds the cast_operator_style_negative_constant and cast_operator_style_from_clause fixtures with snapshots generated from a real test run.

Running the Postgres regression statements through the formatter with castStyle: "operator" found 63 failing statements across the Postgres 15, 16, and 17 suites, all from these two causes. With this change, none fail.

Test:

cargo test -p pgls_pretty_print

[psteinroe]

thank you!