Fix typos and use more idiomatic assertions (#7755)

I have changed `assert!(a == b)` calls to `assert_eq!(a, b)`, which give
better error messages. Similarly for `assert!(a != b)` and
`assert_ne!(a, b)`. Basically all instances were comparing primitives
(string slices or integers), so there is no loss of generality from
special-case macros,

I have also fixed a number of typos in comments, variable names, and a
few user-facing messages.

crates/nu-path/src/tilde.rs

@@ -168,7 +168,7 @@ mod tests {
     fn check_not_expanded(s: &str) {
         let home = PathBuf::from("/home");
         let expanded = expand_tilde_with_home(Path::new(s), Some(home));
-        assert!(expanded == Path::new(s));
+        assert_eq!(expanded, Path::new(s));
     }
 
     #[test]