feat(data/int/basic): add `nat_abs_eq_nat_abs_iff_*` lemmas for nonnegative and nonpositive arguments (#10611)
feat(data/int/basic): add `nat_abs_eq_nat_abs_iff_*` lemmas for nonnegative and nonpositive arguments (#10611)




Co-authored-by: Eric Wieser <da64e90baec5d084ce3d8e05f3b022ae6d118ff5@gmail.com>

leanprover-community/mathlib,leanprover-community/mathlib