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/src/network/url/encode.rs

@@ -81,7 +81,7 @@ impl Command for SubCommand {
                 }),
             },
             Example {
-                description: "Encode all non anphanumeric chars with all flag",
+                description: "Encode all non alphanumeric chars with all flag",
                 example: "'https://example.com/foo bar' | url encode --all",
                 result: Some(Value::test_string("https%3A%2F%2Fexample%2Ecom%2Ffoo%20bar")),
             },