getcolumnmeta should probably be a method on PDOPostgres

### Description

https://www.php.net/manual/en/pdostatement.getcolumnmeta.php


```
	if (!stmt->methods->get_column_meta) {
		pdo_raise_impl_error(stmt->dbh, stmt, "IM001", "driver doesn't support meta data");
		RETURN_FALSE;
	}
```

Though this might be out of scope for the RFC - as I can't design apis.