So that when we later add support for revisions we can use the same
syntax for revisions as elsewhere.
This also prevents people from making typos for commands since
`src/tools/compiletest/src/directives/directive_names.rs` will catch such
typos now.
Note that we one FIXME for a non-trivial change for later:
```
// FIXME(148097): Change `// cdb-checksimple_closure` to `//@ cdb-check:simple_closure`
```
To make debugger stepping intuitive with `-Copt-level=0`. See the
adjusted `basic-stepping.rs` test.
This is kind of a revert of bd0aae92dc, except we don't revert it,
we just make it conditional on `opt-level`. That commit regressed
`basic-stepping.rs`, but it was not noticed since that test did not
exist back then. I have retroactively bisected to find that out.
It seems messy to sprinkle if-cases inside of the
`write_operand_repeatedly()` so make the whole function conditional.
The test that bd0aae92dc added in
`tests/codegen/issues/issue-111603.rs` already use `-Copt-level=3`, so
we don't need to adjust the compiler flags for it to keep passing.
