Backport: Fix threaded FastBroadcast for VectorOfArray #1223

Job	Run time
DiffEqSensitivity.jl/Core/1	35m 40s
DiffEqBase.jl/Downstream/1	55s
DelayDiffEq.jl/Interface/1	48s
SciMLSensitivity.jl/Core2/1	1h 5m 5s
DiffEqBase.jl/Core/1	49s
SciMLSensitivity.jl/Core1/1	1h 2m 20s
SciMLSensitivity.jl/Core3/1	1h 22m 16s
SciMLSensitivity.jl/Core4/1	34m 57s
DiffEqBase.jl/Downstream2/1	50s
OrdinaryDiffEq.jl/Interface/1	38m 9s
SciMLBase.jl/Core/1	7m 53s
OrdinaryDiffEq.jl/Core/1	15m 7s
SciMLSensitivity.jl/Core5/1	1h 58m 0s
SciMLSensitivity.jl/Core6/1	1h 5m 54s
LabelledArrays.jl/RecursiveArrayTools/1	8m 32s
	8h 57m 15s

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