chore: use inline formatting

Minor cleanup using clippy autofix.  This makes the code a bit more readable, and helps spot a few inefficiencies and possible bugs.

```
cargo clippy --fix --workspace -- -A clippy::all -W clippy::uninlined_format_args && cargo fmt
```

tests/by-util/test_csplit.rs

@@ -1457,7 +1457,7 @@ fn create_named_pipe_with_writer(path: &str, data: &str) -> std::process::Child
     nix::unistd::mkfifo(path, nix::sys::stat::Mode::S_IRWXU).unwrap();
     std::process::Command::new("sh")
         .arg("-c")
-        .arg(format!("printf '{}' > {path}", data))
+        .arg(format!("printf '{data}' > {path}"))
         .spawn()
         .unwrap()
 }