Fix a bunch of typo

This PR will fix some typos detected by [typos].

I only picked the ones I was sure were spelling errors to fix, mostly in
the comments.

[typos]: https://github.com/crate-ci/typos

compiler/rustc_resolve/src/lib.rs

@@ -1991,7 +1991,7 @@ impl<'a> Resolver<'a> {
                         _ => panic!("invalid arg index"),
                     }
                 }
-                // Cache the lookup to avoid parsing attributes for an iterm multiple times.
+                // Cache the lookup to avoid parsing attributes for an item multiple times.
                 self.legacy_const_generic_args.insert(def_id, Some(ret.clone()));
                 return Some(ret);
             }