Add tests for Ensemble Problems #1423

Job	Run time
test (Core, 1, ubuntu-latest)	26m 37s
test (Core, 1, macos-latest)	11m 35s
test (Core, 1, windows-latest)	36m 52s
test (Downstream, 1, ubuntu-latest)	9m 8s
test (Downstream, 1, macos-latest)	6m 12s
test (Downstream, 1, windows-latest)	12m 40s
test (Misc, 1, ubuntu-latest)	18m 55s
test (Misc, 1, macos-latest)	9m 10s
test (Misc, 1, windows-latest)	22m 16s
test (Wrappers, 1, ubuntu-latest)	10m 24s
test (Wrappers, 1, macos-latest)	7m 11s
test (Wrappers, 1, windows-latest)	21m 25s
	3h 12m 25s

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