Tests

Add support for undef initializer in `ArrayPartition` #285

Job	Run time
Tests (lts, JET) / Tests - JET	2m 33s
Tests (1, JET) / Tests - JET	5m 10s
Tests (pre, JET) / Tests - JET	7m 2s
Tests (1, Downstream) / Tests - Downstream	19m 14s
Tests (pre, Downstream) / Tests - Downstream	20m 15s
Tests (pre, Core) / Tests - Core	7m 16s
Tests (lts, Core) / Tests - Core	4m 1s
Tests (lts, Downstream) / Tests - Downstream	10m 5s
Tests (1, Core) / Tests - Core	7m 50s
	1h 23m 26s

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