The inspector now supports converting degrees to radians automatically when
using the `radians` hint, so all those utility bindings were redundant.
This cleans things up by making these properties with slash properly bound
to `set_param`/`get_param` which the users can call with the relevant enum.
This is a legacy of Godot 2 days before the inspector had support for groups.
"Properties" with a slash in their name can't be accessed from script unless
using `set()`/`get()` so they were not actual properties as far as script
languages are concerned.
Part of #17558.
