Identical arguments on assert macro family
Lint when identical args are used on `assert_eq!`, `debug_assert_eq!`, `assert_ne!` and `debug_assert_ne!` macros.
Added to the lint `eq_op`.
Common functions added to `utils/higher.rs`
Fixes: #3574Fixes: #4694
changelog: Lint on identical args when calling `assert_eq!`, `debug_assert_eq!`, `assert_ne!` and `debug_assert_ne!` macros