Column name checks are too strict

I think we should not care much about the column names, we already check the column types, which is fine.

```sql
 create table t1(a int);

 insert into t1 VALUES (1);
 copy t1 to '/tmp/data.parquet';

create table t2(b int);
copy t2 from '/tmp/data.parquet';
ERROR:  column "b" is not found in parquet file
```
