mathlib

002b8d97 - feat(algebra/group_with_zero/basic): mul_{left,right}_eq_self₀ (#11069)

feat(algebra/group_with_zero/basic): mul_{left,right}_eq_self₀ (#11069) Defined on `cancel_monoid_with_zero`, copying the name and proofs from `{left,right)_cancel_monoid`s,