chore(data/{int,nat}/modeq): Rationalise lemma names (#17902)
Quite a few `modeq` lemmas are still called `nat.modeq.modeq_something` or `int.modeq.modeq_something`. I'm deleting the duplicated `modeq`, so that lemmas (usually) become `nat.modeq.something` and `int.modeq.something`.
Also add `nat.modeq.eq_of_lt_of_lt` as a corollary to `nat.modeq.eq_of_abs_lt`.
