Tests

refactor: change problem constructors to `XProblem(sys, op[, tspan])` #2016

Job	Run time
Tests (pre, Extended) / Tests - Extended	14m 28s
Tests (1, Initialization) / Tests - Initialization	35m 47s
Tests (lts, RegressionI) / Tests - RegressionI	28s
Tests (lts, InterfaceII) / Tests - InterfaceII	34s
Tests (pre, InterfaceI) / Tests - InterfaceI	14m 23s
Tests (pre, Initialization) / Tests - Initialization	14m 8s
Tests (lts, Downstream) / Tests - Downstream	28s
Tests (pre, Downstream) / Tests - Downstream	14m 55s
Tests (1, Downstream) / Tests - Downstream	15m 12s
Tests (1, InterfaceII) / Tests - InterfaceII	40m 5s
Tests (lts, InterfaceI) / Tests - InterfaceI	30s
Tests (1, InterfaceI) / Tests - InterfaceI	43m 5s
Tests (lts, Extensions) / Tests - Extensions	34s
Tests (1, Extensions) / Tests - Extensions	24m 33s
Tests (pre, FMI) / Tests - FMI	14m 52s
Tests (1, Extended) / Tests - Extended	19m 28s
Tests (lts, Initialization) / Tests - Initialization	31s
Tests (pre, Extensions) / Tests - Extensions	14m 23s
Tests (lts, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	35s
Tests (1, RegressionI) / Tests - RegressionI	16m 5s
Tests (pre, RegressionI) / Tests - RegressionI	14m 34s
Tests (1, FMI) / Tests - FMI	25m 19s
Tests (1, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	21m 30s
Tests (lts, Extended) / Tests - Extended	30s
Tests (lts, FMI) / Tests - FMI	28s
Tests (pre, InterfaceII) / Tests - InterfaceII	14m 50s
Tests (pre, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	14m 15s
	6h 16m 30s

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