Collect methods introduced in self (without inits)

Property definitions

nitc :: model_collect $ MModule :: collect_intro_methods
	# Collect methods introduced in `self` (without inits)
	fun collect_intro_methods(filter: nullable ModelFilter): Set[MMethod] do
		var res = new HashSet[MMethod]
		for mproperty in collect_intro_mproperties(filter) do
			if mproperty isa MMethod and not mproperty.is_init then res.add(mproperty)
		end
		return res
	end
src/model/model_collect.nit:623,2--630,4