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-command/src/env/config/config_env.rs

@@ -57,7 +57,7 @@ impl Command for ConfigEnv {
 
         let env_vars_str = env_to_strings(engine_state, stack)?;
         let nu_config = match engine_state.get_config_path("env-path") {
-            Some(path) => path.clone(),
+            Some(path) => path,
             None => {
                 return Err(ShellError::GenericError {
                     error: "Could not find $nu.env-path".into(),

crates/nu-command/src/env/config/config_nu.rs

@@ -61,7 +61,7 @@ impl Command for ConfigNu {
 
         let env_vars_str = env_to_strings(engine_state, stack)?;
         let nu_config = match engine_state.get_config_path("config-path") {
-            Some(path) => path.clone(),
+            Some(path) => path,
             None => {
                 return Err(ShellError::GenericError {
                     error: "Could not find $nu.config-path".into(),

crates/nu-command/src/env/config/utils.rs

@@ -1,10 +1,10 @@
 use crate::ExternalCommand;
 use nu_protocol::{OutDest, Span, Spanned};
-use std::{collections::HashMap, path::PathBuf};
+use std::{collections::HashMap, path::Path};
 
 pub(crate) fn gen_command(
     span: Span,
-    config_path: PathBuf,
+    config_path: &Path,
     item: String,
     config_args: Vec<String>,
     env_vars_str: HashMap<String, String>,