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/alias.rs

@@ -92,7 +92,7 @@ fn alias_wont_recurse() {
 #[test]
 fn alias_wont_recurse2() {
     Playground::setup("alias_wont_recurse2", |dirs, sandbox| {
-        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+        sandbox.with_files(&[FileWithContentToBeTrimmed(
             "spam.nu",
             r#"
                 def eggs [] { spam 'eggs' }