chore: a few minor lints

I ran this locally, using current main version of clippy:

```bash
cargo dev lint path/to/coreutils -- --workspace --all-features
```

Author: nyurik

src/uu/cp/src/cp.rs

@@ -1113,7 +1113,7 @@ impl Options {
                 });
             }
         }
-        overriding_order.sort_by(|a, b| a.0.cmp(&b.0));
+        overriding_order.sort_by_key(|a| a.0);
 
         let mut attributes = Attributes::NONE;
 

src/uu/fmt/src/parasplit.rs

@@ -421,13 +421,9 @@ impl Iterator for ParagraphStream<'_> {
 
         let mut in_mail = false;
         let mut second_done = false; // for when we use crown or tagged mode
-        loop {
+        while let Some(Line::FormatLine(fl)) = self.lines.peek() {
             // peek ahead
             // need to explicitly force fl out of scope before we can call self.lines.next()
-            let Some(Line::FormatLine(fl)) = self.lines.peek() else {
-                break;
-            };
-
             if p_lines.is_empty() {
                 // first time through the loop, get things set up
                 // detect mail header

src/uu/ls/src/ls.rs

@@ -3579,8 +3579,7 @@ fn get_security_context<'a>(
         };
 
         return uucore::smack::get_smack_label_for_path(&target_path)
-            .map(Cow::Owned)
-            .unwrap_or(Cow::Borrowed(SUBSTITUTE_STRING));
+            .map_or(Cow::Borrowed(SUBSTITUTE_STRING), Cow::Owned);
     }
 
     Cow::Borrowed(SUBSTITUTE_STRING)

src/uucore/src/lib/features/checksum/mod.rs

@@ -543,10 +543,7 @@ pub fn sanitize_sha2_sha3_length_str(algo_kind: AlgoKind, length: &str) -> UResu
 pub fn unescape_filename(filename: &[u8]) -> (Vec<u8>, &'static str) {
     let mut unescaped = Vec::with_capacity(filename.len());
     let mut byte_iter = filename.iter().peekable();
-    loop {
-        let Some(byte) = byte_iter.next() else {
-            break;
-        };
+    while let Some(byte) = byte_iter.next() {
         if *byte == b'\\' {
             match byte_iter.next() {
                 Some(b'\\') => unescaped.push(b'\\'),