Tweak comments in `renames_map_3_to_4` & reorder

Generally moves comments and some entries around, as well as fixing typos and miscellaneous inconsistencies.

To go more in detail on a few things:
- In comments, separate between class names and notes with "--";
- In comments, replace all "broke" with "-- Breaks"
- Moves `@GlobalScope` constants to its own group in `enum_renames`
- Move `{ "remove", "remove_at" },` underneath the Builtin Types methods.
- Move C#'s `AddNode3dGizmoPlugin` to where it should be, in alphabetical order.
- Give more details to some class renames.
- Comments out `remove` -> `remove_at`