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/integer-cmp.rs

@@ -10,19 +10,19 @@ use std::cmp::Ordering;
 // CHECK-LABEL: @cmp_signed
 #[no_mangle]
 pub fn cmp_signed(a: i64, b: i64) -> Ordering {
-// CHECK: icmp slt
-// CHECK: icmp ne
-// CHECK: zext i1
-// CHECK: select i1
+    // CHECK: icmp slt
+    // CHECK: icmp ne
+    // CHECK: zext i1
+    // CHECK: select i1
     a.cmp(&b)
 }
 
 // CHECK-LABEL: @cmp_unsigned
 #[no_mangle]
 pub fn cmp_unsigned(a: u32, b: u32) -> Ordering {
-// CHECK: icmp ult
-// CHECK: icmp ne
-// CHECK: zext i1
-// CHECK: select i1
+    // CHECK: icmp ult
+    // CHECK: icmp ne
+    // CHECK: zext i1
+    // CHECK: select i1
     a.cmp(&b)
 }