gcongr attributes for lemmas up in the import chain

In this file we add gcongr attribute to lemmas in Lean.Init. We may add lemmas from other files imported by Mathlib/Tactic/GCongr/Core later.

theorem imp_trans {a b c : Prop} (h : a → b) : (b → c) → a → c

theorem imp_trans' {a b c : Prop} (h : b → c) : (a → b) → a → c