Have clippy warn about uninlined format arguments

This makes clippy warn about `format!("{}", var)`, with a
machine-applicable fix converting to `format!("{var}")`.

Cargo.toml

@@ -80,6 +80,7 @@ string_lit_as_bytes = "warn"
 string_to_string = "warn"
 todo = "warn"
 trait_duplication_in_bounds = "warn"
+uninlined_format_args = "warn"
 verbose_file_reads = "warn"
 wildcard_imports = "warn"
 zero_sized_map_values = "warn"