Use variable names directly in the format strings (#7906)

# Description

Lint: `clippy::uninlined_format_args`

More readable in most situations.
(May be slightly confusing for modifier format strings
https://doc.rust-lang.org/std/fmt/index.html#formatting-parameters)

Alternative to #7865

# User-Facing Changes

None intended

# Tests + Formatting

(Ran `cargo +stable clippy --fix --workspace -- -A clippy::all -D
clippy::uninlined_format_args` to achieve this. Depends on Rust `1.67`)

crates/nu-command/tests/commands/roll.rs

@@ -97,7 +97,7 @@ mod columns {
 
         let actual = nu!(
             cwd: ".",
-            format!("{} | roll right --by 3 --cells-only | columns | str join '-' ", four_bitstring)
+            format!("{four_bitstring} | roll right --by 3 --cells-only | columns | str join '-' ")
         );
 
         assert_eq!(actual.out, expected_value.1);
@@ -142,12 +142,11 @@ mod columns {
         "#,
         );
         println!(
-            "{} | roll left --by 3 | {}",
-            bitstring_as_nu_row_pipeline, nu_row_literal_bitstring_to_decimal_value_pipeline
+            "{bitstring_as_nu_row_pipeline} | roll left --by 3 | {nu_row_literal_bitstring_to_decimal_value_pipeline}"
         );
         nu!(
             cwd: ".",
-            format!("{} | roll left --by 3 | {}", bitstring_as_nu_row_pipeline, nu_row_literal_bitstring_to_decimal_value_pipeline)
+            format!("{bitstring_as_nu_row_pipeline} | roll left --by 3 | {nu_row_literal_bitstring_to_decimal_value_pipeline}")
         ).out
     }