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/debug-compile-unit-path.rs

@@ -3,7 +3,7 @@
 //
 // Ensure that we remap the compile unit directory and that we set it to the compilers current
 // working directory and not something else.
-#![crate_type="rlib"]
+#![crate_type = "rlib"]
 
 // CHECK-DAG: [[FILE:![0-9]*]] = !DIFile(filename: "/base/debug-compile-unit-path.rs{{.*}}", directory: "/cwd/")
 // CHECK-DAG: {{![0-9]*}} = distinct !DICompileUnit({{.*}}file: [[FILE]]