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-command/tests/commands/network/port.rs

@@ -41,7 +41,7 @@ fn port_with_already_usage() {
             return;
         }
     }
-    panic!("already check port report AddrInUse for seveval times, but still failed.");
+    panic!("already check port report AddrInUse for several times, but still failed.");
 }
 
 #[test]