Fix PostgreSQL 18 compatibility issues related to "?column?" names in…

[gurkanindibay]

… subqueries

• Updated various planner and deparser files to handle NULL or "?column?" as resname by generating meaningful column names.
• Ensured that generated names follow a consistent format to avoid parsing errors in complex queries.
• Added debug queries and tests to isolate and reproduce the issues related to intermediate results and subqueries.
• Created setup scripts for test tables and data to facilitate regression testing for PostgreSQL 18 compatibility.

DESCRIPTION: PR description that will go into the change log, up to 78 characters

[gurkanindibay]

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[gurkanindibay]

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[m3hm3t]

Thanks for your support.

Would you be able to identify the PostgreSQL commit that introduced this behavior?