Add tests for LinearExponential() on GPU #4701

Job	Run time
DelayDiffEq.jl/Interface/1	19m 42s
DelayDiffEq.jl/Integrators/1	13m 33s
DelayDiffEq.jl/Regression/1	14m 38s
StochasticDiffEq.jl/Interface1/1	32m 57s
StochasticDiffEq.jl/Interface2/1	27m 46s
StochasticDiffEq.jl/Interface3/1	24m 41s
StochasticDiffEq.jl/AlgConvergence/1	21m 48s
DiffEqCallbacks.jl/All/1	29m 55s
SciMLSensitivity.jl/Core1/1	49m 53s
SciMLSensitivity.jl/Core2/1	46m 40s
SciMLSensitivity.jl/Core3/1	46m 27s
SciMLSensitivity.jl/Core4/1	42m 17s
SciMLSensitivity.jl/Core5/1	45m 24s
ModelingToolkit.jl/All/1	40m 0s
DiffEqDevTools.jl/Core/1	35m 26s
ProbNumDiffEq.jl/Downstream/1	40m 56s
PositiveIntegrators.jl/Downstream/1	41m 13s
	9h 33m 16s

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