Tests

Port v3 RaggedEnd for per-column end in ragged arrays #401

Job	Run time
Tests (lts, nopre) / Tests - nopre	3m 22s
Tests (1, nopre) / Tests - nopre	5m 48s
Tests (pre, Core) / Tests - Core	6m 25s
Tests (1, Core) / Tests - Core	5m 1s
Tests (pre, Downstream) / Tests - Downstream	1m 3s
Tests (1, Downstream) / Tests - Downstream	2m 26s
Tests (lts, Core) / Tests - Core	4m 19s
Tests (lts, Downstream) / Tests - Downstream	1m 0s
	29m 24s

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