streaming: fix hash join degree table scan

[skyzh]

             let mut table_data = vec![];
             let mut degree_table_data = vec![];

             #[for_await]
             for x in table_iter {
                 table_data.push(x?);
             }

             #[for_await]
             for x in degree_table_iter {
                 degree_table_data.push(x?);
             }

Now we fetch ALL the data before start processing, instead of fetch-while-processing.

Part of #5977, can be fixed after the compiler bug is fixed.

[skyzh]

Can be fixed by bumping the toolchain as the upstream PR has been merged. Anyone interested in this issue can work on it.