feat(order/hom/basic): some lemmas about order homs and equivs  (#14872)
feat(order/hom/basic): some lemmas about order homs and equivs  (#14872)

A few lemmas from #11053, which I have seperated from the original PR following @riccardobrasca's suggestion. 

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





leanprover-community/mathlib,leanprover-community/mathlib