Split out OrdinaryDiffEqCore and make dependencies into a tree #3735

Job	Run time
test (InterfaceI, 1)	20m 50s
test (InterfaceII, 1)	24m 40s
test (InterfaceIII, 1)	16m 22s
test (Integrators_I, 1)	21m 23s
test (AlgConvergence_I, 1)	11m 35s
test (AlgConvergence_II, 1)	9m 27s
test (AlgConvergence_III, 1)	12m 43s
test (Downstream, 1)	11m 25s
test (ODEInterfaceRegression, 1)	12m 23s
test (Multithreading, 1)	13m 46s
test (OrdinaryDiffEqAdamsBashforthMoulton, 1)	11m 8s
test (OrdinaryDiffEqBDF, 1)	16m 41s
test (OrdinaryDiffEqCore, 1)	9m 49s
test (OrdinaryDiffEqDefault, 1)	10m 0s
test (OrdinaryDiffEqDifferentiation, 1)	9m 37s
test (OrdinaryDiffEqExplicitRK, 1)	9m 13s
test (OrdinaryDiffEqExponentialRK, 1)	12m 36s
test (OrdinaryDiffEqExtrapolation, 1)	12m 1s
test (OrdinaryDiffEqFIRK, 1)	11m 47s
test (OrdinaryDiffEqFeagin, 1)	11m 42s
test (OrdinaryDiffEqFunctionMap, 1)	9m 53s
test (OrdinaryDiffEqHighOrderRK, 1)	10m 38s
test (OrdinaryDiffEqIMEXMultistep, 1)	9m 47s
test (OrdinaryDiffEqLinear, 1)	11m 43s
test (OrdinaryDiffEqLowOrderRK, 1)	13m 55s
test (OrdinaryDiffEqLowStorageRK, 1)	16m 44s
test (OrdinaryDiffEqNordsieck, 1)	10m 50s
test (OrdinaryDiffEqPDIRK, 1)	9m 50s
test (OrdinaryDiffEqPRK, 1)	9m 38s
test (OrdinaryDiffEqQPRK, 1)	10m 51s
test (OrdinaryDiffEqRKN, 1)	12m 30s
test (OrdinaryDiffEqRosenbrock, 1)	16m 5s
test (OrdinaryDiffEqSDIRK, 1)	9m 49s
test (OrdinaryDiffEqSSPRK, 1)	14m 17s
test (OrdinaryDiffEqStabilizedIRK, 1)	10m 44s
test (OrdinaryDiffEqStabilizedRK, 1)	11m 38s
test (OrdinaryDiffEqSymplecticRK, 1)	18m 8s
test (OrdinaryDiffEqTsit5, 1)	9m 41s
test (OrdinaryDiffEqVerner, 1)	9m 38s
	8h 15m 27s

Provide feedback