Avoid taking unnecessary ownership of intermediates (#12740)

# Description

Judiciously try to avoid allocations/clone by changing the signature of
functions

- **Don't pass str by value unnecessarily if only read**
- **Don't require a vec in `Sandbox::with_files`**
- **Remove unnecessary string clone**
- **Fixup unnecessary borrow**
- **Use `&str` in shape color instead**
- **Vec -> Slice**
- **Elide string clone**
- **Elide `Path` clone**
- **Take &str to elide clone in tests**

# User-Facing Changes
None

# Tests + Formatting
This touches many tests purely in changing from owned to borrowed/static
data

crates/nu-color-config/src/color_config.rs

@@ -13,7 +13,7 @@ pub fn lookup_ansi_color_style(s: &str) -> Style {
             .and_then(|c| c.map(|c| c.normal()))
             .unwrap_or_default()
     } else if s.starts_with('{') {
-        color_string_to_nustyle(s.to_string())
+        color_string_to_nustyle(s)
     } else {
         lookup_style(s)
     }
@@ -74,13 +74,13 @@ fn get_style_from_value(record: &Record) -> Option<NuStyle> {
     }
 }
 
-fn color_string_to_nustyle(color_string: String) -> Style {
+fn color_string_to_nustyle(color_string: &str) -> Style {
     // eprintln!("color_string: {}", &color_string);
     if color_string.is_empty() {
         return Style::default();
     }
 
-    let nu_style = match nu_json::from_str::<NuStyle>(&color_string) {
+    let nu_style = match nu_json::from_str::<NuStyle>(color_string) {
         Ok(s) => s,
         Err(_) => return Style::default(),
     };
@@ -97,13 +97,13 @@ mod tests {
     #[test]
     fn test_color_string_to_nustyle_empty_string() {
         let color_string = String::new();
-        let style = color_string_to_nustyle(color_string);
+        let style = color_string_to_nustyle(&color_string);
         assert_eq!(style, Style::default());
     }
 
     #[test]
     fn test_color_string_to_nustyle_valid_string() {
-        let color_string = r#"{"fg": "black", "bg": "white", "attr": "b"}"#.to_string();
+        let color_string = r#"{"fg": "black", "bg": "white", "attr": "b"}"#;
         let style = color_string_to_nustyle(color_string);
         assert_eq!(style.foreground, Some(Color::Black));
         assert_eq!(style.background, Some(Color::White));
@@ -112,7 +112,7 @@ mod tests {
 
     #[test]
     fn test_color_string_to_nustyle_invalid_string() {
-        let color_string = "invalid string".to_string();
+        let color_string = "invalid string";
         let style = color_string_to_nustyle(color_string);
         assert_eq!(style, Style::default());
     }

crates/nu-color-config/src/shape_color.rs

@@ -3,8 +3,8 @@ use nu_ansi_term::{Color, Style};
 use nu_protocol::{Config, Value};
 
 // The default colors for shapes, used when there is no config for them.
-pub fn default_shape_color(shape: String) -> Style {
-    match shape.as_ref() {
+pub fn default_shape_color(shape: &str) -> Style {
+    match shape {
         "shape_and" => Style::new().fg(Color::Purple).bold(),
         "shape_binary" => Style::new().fg(Color::Purple).bold(),
         "shape_block" => Style::new().fg(Color::Blue).bold(),
@@ -45,8 +45,8 @@ pub fn default_shape_color(shape: String) -> Style {
     }
 }
 
-pub fn get_shape_color(shape: String, conf: &Config) -> Style {
-    match conf.color_config.get(shape.as_str()) {
+pub fn get_shape_color(shape: &str, conf: &Config) -> Style {
+    match conf.color_config.get(shape) {
         Some(int_color) => {
             // Shapes do not use color_config closures, currently.
             match int_color {