Tests

refactor: change problem constructors to `XProblem(sys, op[, tspan])` #2019

Job	Run time
Tests (lts, Downstream) / Tests - Downstream	31s
Tests (1, Initialization) / Tests - Initialization	34m 18s
Tests (lts, Extensions) / Tests - Extensions	30s
Tests (lts, RegressionI) / Tests - RegressionI	34s
Tests (1, Extended) / Tests - Extended	19m 36s
Tests (pre, InterfaceI) / Tests - InterfaceI	14m 9s
Tests (pre, Initialization) / Tests - Initialization	14m 6s
Tests (lts, Extended) / Tests - Extended	31s
Tests (lts, FMI) / Tests - FMI	30s
Tests (pre, Extended) / Tests - Extended	14m 28s
Tests (pre, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	14m 22s
Tests (1, RegressionI) / Tests - RegressionI	15m 39s
Tests (pre, FMI) / Tests - FMI	14m 5s
Tests (1, InterfaceI) / Tests - InterfaceI	42m 27s
Tests (1, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	20m 46s
Tests (1, Extensions) / Tests - Extensions	24m 6s
Tests (lts, InterfaceII) / Tests - InterfaceII	30s
Tests (pre, Extensions) / Tests - Extensions	13m 57s
Tests (pre, RegressionI) / Tests - RegressionI	14m 28s
Tests (pre, Downstream) / Tests - Downstream	14m 27s
Tests (1, InterfaceII) / Tests - InterfaceII	39m 35s
Tests (1, Downstream) / Tests - Downstream	15m 4s
Tests (lts, Initialization) / Tests - Initialization	31s
Tests (pre, InterfaceII) / Tests - InterfaceII	14m 32s
Tests (1, FMI) / Tests - FMI	26m 0s
Tests (lts, InterfaceI) / Tests - InterfaceI	30s
Tests (lts, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	34s
	6h 10m 46s

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