Make copium with dict memo semantically equivalent to stdlib #34

Acknowledged Regression: -13.98%

⚡ 1 improved benchmark
❌ 1 (👁 1) regressed benchmark
✅ 356 untouched benchmarks

	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	`test_combined_cases[copium-all_reflexive]`	33.3 µs	22.2 µs	+49.53%
👁	`test_individual_cases[copium-cpython:91610:repeating_atomic]`	22.9 µs	26.6 µs	-13.98%

_{Comparing equivalent-reduce-handling (207cec7) with main (68cd2fe)}