This makes code more readale and concise,
moving all format arguments like `format!("{}", foo)`
into the more compact `format!("{foo}")` form.
The change was automatically created with, so there are far less change
of an accidental typo.
```
cargo clippy --fix -- -A clippy::all -W clippy::uninlined_format_args
```
Otherwise, fall back to the multi ABI scheme, except in testing, where
it becomes a hard error.
This should make it possible to use a rustup-provided rust-analyzer with
proc macro dylibs compiled by older rustcs, and it'll also catch changes
to the format of `rustc --version` or the `.rustc` section that would
make them impossible to compare for equality.
