Fix column list comparison in transmit format
As noticed in #1718 the cache might not reload the cache files when new columns were added.
This is because of an issue in `transmit_format` where the column list comparison fails because the order was not deterministic. This causes the `transmit_format` to apply an unnecessary `set_format` transform with shuffled column names.

I fixed that by sorting the columns for the comparison and added a test.

To properly test that I added a third column `col_3` to the dummy_dataset used for tests.