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`
```
While looking at the pretty-printers, I found a few minor oddities in
StdNonZeroNumberProvider.
First, gdb.Type.fields() already returns a sequence, so there's no
need to call list().
Second, it's more idiomatic for the (somewhat misnamed) to_string
method to simply return the underlying gdb.Value. This also lets gdb
apply whatever formats were passed to `print`, as the new test shows.
Third, there's no need to use the field's name when looking up a field
in a value, the gdb.Field itself can be used.
This is to unblock the tree, a proper fix will need to be investigated.
I think the debuginfo test suite supports revisions, however debugger
directives do not respect such revisions, which is problematic.
It's that 32-bit and 64-bit msvc of course have different integer widths
for `isize` and `usize`, meaning their underlying integer is different
and thus printed differently.
