Tests

Fix @mtkmodel to work without using ModelingToolkit #1963

Job	Run time
Tests (pre, RegressionI) / Tests - RegressionI	14m 42s
Tests (lts, FMI) / Tests - FMI	17m 39s
Tests (lts, Downstream) / Tests - Downstream	16m 24s
Tests (1, Initialization) / Tests - Initialization	31m 34s
Tests (1, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	20m 36s
Tests (1, FMI) / Tests - FMI	25m 20s
Tests (1, InterfaceII) / Tests - InterfaceII	43m 34s
Tests (1, InterfaceI) / Tests - InterfaceI	42m 34s
Tests (1, RegressionI) / Tests - RegressionI	15m 55s
Tests (lts, RegressionI) / Tests - RegressionI	7m 49s
Tests (1, Extensions) / Tests - Extensions	45m 2s
Tests (1, Extended) / Tests - Extended	19m 21s
Tests (pre, Initialization) / Tests - Initialization	14m 39s
Tests (pre, InterfaceI) / Tests - InterfaceI	15m 31s
Tests (lts, InterfaceII) / Tests - InterfaceII	39m 47s
Tests (pre, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	17m 45s
Tests (lts, Initialization) / Tests - Initialization	21m 27s
Tests (pre, InterfaceII) / Tests - InterfaceII	14m 39s
Tests (pre, Extended) / Tests - Extended	14m 23s
Tests (pre, Extensions) / Tests - Extensions	14m 18s
Tests (pre, FMI) / Tests - FMI	14m 13s
Tests (1, Downstream) / Tests - Downstream	27m 49s
Tests (lts, Extended) / Tests - Extended	11m 7s
Tests (pre, Downstream) / Tests - Downstream	14m 46s
Tests (lts, Extensions) / Tests - Extensions	29m 47s
Tests (lts, SymbolicIndexingInterface) / Tests - SymbolicIndexingInterface	11m 49s
Tests (lts, InterfaceI) / Tests - InterfaceI	32m 52s
	9h 55m 22s

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