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`
```
Disabling loading of pretty printers in the debugger itself is more
reliable. Before this commit the .gdb_debug_scripts section couldn't be
included in dylibs or rlibs as otherwise there is no way to disable the
section anymore without recompiling the entire standard library.
Like #107044, this will let us track compatibility with LLVM 16 going
forward, especially after we eventually upgrade our own to the next.
This also drops `tidy` here and in `x86_64-gnu-llvm-15`, syncing with
that change in #106085.
