Deref &String arguments to &str where appropriate (#10321)

# Description
This generally makes for nicer APIs, as you are not forced to use an
existing allocation covering the full `String`.

Some exceptions remain where the underlying type requirements favor it.

# User-Facing Changes
None

crates/nu-protocol/src/engine/stack.rs

@@ -376,8 +376,8 @@ impl Stack {
         engine_state.env_vars.contains_key(name)
     }
 
-    pub fn is_overlay_active(&self, name: &String) -> bool {
-        self.active_overlays.contains(name)
+    pub fn is_overlay_active(&self, name: &str) -> bool {
+        self.active_overlays.iter().any(|n| n == name)
     }
 
     pub fn add_overlay(&mut self, name: String) {
@@ -385,7 +385,7 @@ impl Stack {
         self.active_overlays.push(name);
     }
 
-    pub fn remove_overlay(&mut self, name: &String) {
+    pub fn remove_overlay(&mut self, name: &str) {
         self.active_overlays.retain(|o| o != name);
     }
 }

crates/nu-protocol/src/eval_const.rs

@@ -7,19 +7,19 @@ use crate::{
     record, HistoryFileFormat, PipelineData, Range, Record, ShellError, Span, Value,
 };
 use nu_system::os_info::{get_kernel_version, get_os_arch, get_os_family, get_os_name};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 pub fn create_nu_constant(engine_state: &EngineState, span: Span) -> Result<Value, ShellError> {
-    fn canonicalize_path(engine_state: &EngineState, path: &PathBuf) -> PathBuf {
+    fn canonicalize_path(engine_state: &EngineState, path: &Path) -> PathBuf {
         let cwd = engine_state.current_work_dir();
 
         if path.exists() {
             match nu_path::canonicalize_with(path, cwd) {
                 Ok(canon_path) => canon_path,
-                Err(_) => path.clone(),
+                Err(_) => path.to_owned(),
             }
         } else {
-            path.clone()
+            path.to_owned()
         }
     }