Update io iterators to produce IoResults

Most IO related functions return an IoResult so that the caller can handle failure
in whatever way is appropriate. However, the `lines`, `bytes`, and `chars` iterators all
supress errors. This means that code that needs to handle errors can't use any of these
iterators. All three of these iterators were updated to produce IoResults.

Fixes #12368

src/test/bench/shootout-k-nucleotide-pipes.rs

@@ -182,7 +182,7 @@ fn main() {
    let mut proc_mode = false;
 
    for line in rdr.lines() {
-       let line = line.trim().to_owned();
+       let line = line.unwrap().trim().to_owned();
 
        if line.len() == 0u { continue; }
 

src/test/bench/sudoku.rs

@@ -72,7 +72,7 @@ impl Sudoku {
 
         let mut g = vec::from_fn(10u, { |_i| ~[0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8] });
         for line in reader.lines() {
-            let comps: ~[&str] = line.trim().split(',').collect();
+            let comps: ~[&str] = line.unwrap().trim().split(',').collect();
 
             if comps.len() == 3u {
                 let row     = from_str::<uint>(comps[0]).unwrap() as u8;