working on FEC tests again

• pass n to try_all_decoding_combinations and don't try to decode when shards have been recoded (\#shards > n) and there are no recoded shards in the k combination under review (\max(is) < n)
• pass recoding_steps and should_not_be_decodable as arguments to end_to_end_with_recoding_template
• fix n = 5 => this leads to tests that run in less than 10sec again
• add (k, n) = (8, 10) => tests still run in less than 13sec
• split recoding scenarii into "simple" and "chain"
• show indices in a "pretty" format, i.e. showing indices greater than n as (n), (n + 1), ...

src/fec.rs

@@ -240,6 +240,7 @@ mod tests {
             &[3, 6, 8, 9, 10],
             &[vec![2, 4, 6], vec![1, 3, 7], vec![6, 7, 8], vec![3, 6, 8]],
         ));
+        assert!(contains_one_of(&[0, 4, 5], &[vec![2, 3, 5], vec![4, 5]]));
     }
 
     fn try_all_decoding_combinations<F: PrimeField>(