Run rustfmt on tests/codegen/.

Except for `simd-intrinsic/`, which has a lot of files containing
multiple types like `u8x64` which really are better when hand-formatted.

There is a surprising amount of two-space indenting in this directory.

Non-trivial changes:
- `rustfmt::skip` needed in `debug-column.rs` to preserve meaning of the
  test.
- `rustfmt::skip` used in a few places where hand-formatting read more
  nicely: `enum/enum-match.rs`
- Line number adjustments needed for the expected output of
  `debug-column.rs` and `coroutine-debug.rs`.

tests/codegen/enum/enum-debug-clike.rs

@@ -17,7 +17,11 @@
 #![allow(unused_variables)]
 #![allow(unused_assignments)]
 
-enum E { A, B, C }
+enum E {
+    A,
+    B,
+    C,
+}
 
 pub fn main() {
     let e = E::C;