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/path.rs

@@ -660,10 +660,10 @@ impl Path {
     /// the current directory.
     ///
     /// * On Unix, a path is absolute if it starts with the root,
-    /// so [`is_absolute`](Path::is_absolute) and [`has_root`](Path::has_root) are equivalent.
+    ///   so [`is_absolute`](Path::is_absolute) and [`has_root`](Path::has_root) are equivalent.
     ///
     /// * On Windows, a path is absolute if it has a prefix and starts with the root:
-    /// `c:\windows` is absolute, while `c:temp` and `\temp` are not.
+    ///   `c:\windows` is absolute, while `c:temp` and `\temp` are not.
     ///
     /// # Examples
     ///