RE: Replace IN VALUES with ANY in WHERE clauses during optimization

Hi Ivan,
I tested the patch using the input provided in commands.sql and observed improvements in both planning and execution time. These optimizations are especially noticeable when working with a mulitple tables. Even when querying just a single table, there is a small improvement in planning and execution time, with differences ranging from 0.02 to 0.04 ms.

CREATE TABLE test_table (
_id SERIAL PRIMARY KEY,
_val TEXT NOT NULL
);

INSERT INTO test_table (_val) VALUES
('a'),
('b'),
('c'),
('d'),
('e');

EXPLAIN ANALYZE
SELECT *
FROM test_table
WHERE _val IN ('b', 'd', 'e');

EXPLAIN ANALYZE
SELECT *
FROM test_table
WHERE _val IN (VALUES ('b'), ('d'), ('e'));

The patch optimizes IN clauses effectively, especially when the syntax uses VALUES.

When writing queries like:
col IN (VALUES ('a'), ('b'), ('c'))

the optimization makes it behave similarly to:
col IN ('a', 'b', 'c')

This leads to faster query execution times and reduced planning overhead.

Best Regards,
PostgreSQL Contributiors - Newt Global
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