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/stack-probes-inline.rs

@@ -27,6 +27,6 @@ trait Sized {}
 
 #[no_mangle]
 pub fn foo() {
-// CHECK: @foo() unnamed_addr #0
-// CHECK: attributes #0 = { {{.*}}"probe-stack"="inline-asm"{{.*}} }
+    // CHECK: @foo() unnamed_addr #0
+    // CHECK: attributes #0 = { {{.*}}"probe-stack"="inline-asm"{{.*}} }
 }