refactor(order/complete_lattice): use `is_empty` (#8796)
* change `set.univ_eq_empty_iff` to use `is_empty`;
* rename `set.range_eq_empty` to `set.range_eq_empty_iff`;
* add new `set.range_eq_empty`, it assumes `[is_empty α]`;
* combine `supr_of_empty`, `supr_of_empty'`, and `supr_empty` into `supr_of_empty`, same for `infi`;
* replace `csupr_neg` with `csupr_of_empty` and `csupr_false`;
* adjust some proofs to use `casesI is_empty_of_nonempty α` instead of `by_cases h : nonempty α`.
