Describe the bug
RowNumber reader that was recently introduced (in #8715) has a bug in ordering row groups - namely it orders them by ordinal, instead of respecting user-requested order.

To Reproduce
The PR that I already prepared has a test case: #8863

Expected behavior
We should respect a user-requested row group order (by user I mean user of the RowNumber reader API, its try_new function).

Additional context