Clippy fixes from stable and nightly (#13455)

- **Doccomment style fixes**
- **Forgotten stuff in `nu-pretty-hex`**
- **Don't `for` around an `Option`**
- and more

I think the suggestions here are a net positive, some of the suggestions
moved into #13498 feel somewhat arbitrary, I also raised
https://github.com/rust-lang/rust-clippy/issues/13188 as the nightly
`byte_char_slices` would require either a global allow or otherwise a
ton of granular allows or possibly confusing bytestring literals.

crates/nu-path/src/tilde.rs

@@ -121,7 +121,7 @@ fn expand_tilde_with_another_user_home(path: &Path) -> PathBuf {
     return match path.to_str() {
         Some(file_path) => {
             let mut file = file_path.to_string();
-            match file_path.find(|c| c == '/' || c == '\\') {
+            match file_path.find(['/', '\\']) {
                 None => {
                     file.remove(0);
                     user_home_dir(&file)