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-test-support/src/macros.rs

@@ -284,7 +284,7 @@ pub fn nu_run_test(opts: NuOpts, commands: impl AsRef<str>, with_std: bool) -> O
         command.arg("--no-std-lib");
     }
     command
-        .arg(format!("-c {}", escape_quote_string(commands)))
+        .arg(format!("-c {}", escape_quote_string(&commands)))
         .stdout(Stdio::piped())
         .stderr(Stdio::piped());
 
@@ -353,7 +353,7 @@ where
             let plugin_path = nu_path::canonicalize_with(&plugin, &test_bins)
                 .unwrap_or_else(|_| panic!("failed to canonicalize plugin {} path", &plugin));
             let plugin_path = plugin_path.to_string_lossy();
-            escape_quote_string(plugin_path.into_owned())
+            escape_quote_string(&plugin_path)
         })
         .collect();
     let plugins_arg = format!("[{}]", plugin_paths_quoted.join(","));
@@ -397,7 +397,7 @@ where
     Outcome::new(out, err.into_owned(), output.status)
 }
 
-fn escape_quote_string(input: String) -> String {
+fn escape_quote_string(input: &str) -> String {
     let mut output = String::with_capacity(input.len() + 2);
     output.push('"');
 

crates/nu-test-support/src/playground/play.rs

@@ -199,7 +199,7 @@ impl<'a> Playground<'a> {
         self
     }
 
-    pub fn with_files(&mut self, files: Vec<Stub>) -> &mut Self {
+    pub fn with_files(&mut self, files: &[Stub]) -> &mut Self {
         let endl = fs::line_ending();
 
         files