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-protocol/src/value/range.rs

@@ -50,7 +50,7 @@ impl Range {
             Ok(Value::Bool { val: true, .. })
         );
 
-        // Convert the next value into the inctement
+        // Convert the next value into the increment
         let incr = if let Value::Nothing { .. } = next {
             if moves_up {
                 Value::int(1i64, expr_span)