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/tests/commands/path/exists.rs

@@ -5,7 +5,7 @@ use nu_test_support::playground::Playground;
 #[test]
 fn checks_if_existing_file_exists() {
     Playground::setup("path_exists_1", |dirs, sandbox| {
-        sandbox.with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(),

crates/nu-command/tests/commands/path/expand.rs

@@ -7,9 +7,7 @@ use std::path::PathBuf;
 #[test]
 fn expands_path_with_dot() {
     Playground::setup("path_expand_1", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -28,9 +26,7 @@ fn expands_path_with_dot() {
 #[test]
 fn expands_path_without_follow_symlink() {
     Playground::setup("path_expand_3", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -49,9 +45,7 @@ fn expands_path_without_follow_symlink() {
 #[test]
 fn expands_path_with_double_dot() {
     Playground::setup("path_expand_2", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -69,9 +63,7 @@ fn expands_path_with_double_dot() {
 #[test]
 fn const_path_expand() {
     Playground::setup("const_path_expand", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -121,9 +113,7 @@ mod windows {
     #[test]
     fn expands_path_without_follow_symlink() {
         Playground::setup("path_expand_3", |dirs, sandbox| {
-            sandbox
-                .within("menu")
-                .with_files(vec![EmptyFile("spam.txt")]);
+            sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
             let cwd = dirs.test();
             std::os::windows::fs::symlink_file(

crates/nu-command/tests/commands/path/type_.rs

@@ -18,9 +18,7 @@ fn returns_type_of_missing_file() {
 #[test]
 fn returns_type_of_existing_file() {
     Playground::setup("path_expand_1", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -37,9 +35,7 @@ fn returns_type_of_existing_file() {
 #[test]
 fn returns_type_of_existing_directory() {
     Playground::setup("path_expand_1", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(
@@ -65,9 +61,7 @@ fn returns_type_of_existing_directory() {
 #[test]
 fn returns_type_of_existing_file_const() {
     Playground::setup("path_type_const", |dirs, sandbox| {
-        sandbox
-            .within("menu")
-            .with_files(vec![EmptyFile("spam.txt")]);
+        sandbox.within("menu").with_files(&[EmptyFile("spam.txt")]);
 
         let actual = nu!(
             cwd: dirs.test(), pipeline(