Introduce AllEquations.lean

[nomeata]

as discussed in https://leanprover.zulipchat.com/#narrow/stream/458659-Equational/topic/Refactoring.20the.20Lean.20file.20structure/near/473253407

[nomeata]

Unfortunately, the file is rather slow. So many operators doing the same type class inference over and over again!

cumulative profiling times:
	attribute application 139ms
	elaboration 15.8s
	fix level params 75ms
	import 65.6ms
	initialization 44.9ms
	instantiate metavars 29.4ms
	interpretation 2.7s
	linting 657ms
	parsing 1.72s
	process pre-definitions 628ms
	share common exprs 138ms
	type checking 346ms
	typeclass inference 85.6s

Maybe the AllEquations file could be rewritten to use inst.op explicitly, for faster processing. Or maybe it's fine as everyone builds this only once anyways.