Premature calculation of actual description when generating matcher description

[jas14]

In cases where the example passes, SuperDiff::RSpec::AugmentedMatcher#description appears to generate the description of the actual object via a call to matcher_text_builder_args:

super_diff/lib/super_diff/rspec/augmented_matcher.rb

Line 43 in 805537f

actual: actual_for_matcher_text,

However, the MatcherTextBuilders::Base#matcher_description doesn't use said description:

super_diff/lib/super_diff/rspec/matcher_text_builders/base.rb

Lines 30 to 39 in 805537f

	def matcher_description
	template =
	MatcherTextTemplate.new do |t|
	t.add_text expected_action_for_description
	add_expected_value_to_description(t)
	add_extra_after_expected_to(t)
	end
	Csi.decolorize(template.to_s(as_single_line: true))
	end

This can incur a substantial delay in cases where the inspection of the actual object takes a lot of time (e.g. #160).