Fix #5853: fully qualify function names inside macros during the binding process

[Mytherin]

Fixes #5853

During binding we extend unqualified function calls with the catalog and schema information of the function we found, e.g.:

CREATE MACRO "sum"(x) AS (CASE WHEN sum(x) IS NULL THEN 0 ELSE sum(x) END);
-- becomes
CREATE MACRO "sum"(x) AS (CASE WHEN system.main.sum(x) IS NULL THEN 0 ELSE system.main.sum(x) END);

This prevents recursive macros from being created, where during initial binding we bind to system.main.sum, but during subsequent binding we bind to the same macro again (db.main.sum).